Alternately, you can use this tool to generate one:
http://tools.trepmal.com/wp-readme-generator/

A readme.txt is needed so your plugin will display correctly in our repository, but also so we can make sure you're providing the users with all the information they need before they install your plugin. Our goal with this is to make sure everyone knows what they're installing and what they need to do before they install it. No surprises :)

This is especially important if your plugin is making calls back to your own servers. For the most part, we do not permit offloading of images or code, however in the case where you are providing a service (like Disqus or Akismet or Twitter), we permit it. The catch is you have to actually explain this to the layman in your readme, so they know where data is going.

Keep in mind, a readme.MD is not the same as a readme.TXT - the formatting for markup is different.

Please send a link so the completed plugin can be downloaded. Alternately you can reply to this and send a .zip or .rar file. As this is for a new plugin request, please reply within seven days of this email or we will reject your plugin.

Sociable continues being the leader in the sharing space of WordPress plugins. Started more than 2 years ago, and with over 1,2mm downloads now, here comes the version 4.0, with everything you expect to get, and then some.

As you can see, we've improved our visual interface, the default icons are now much more appealing, and a touch bit larger (you do want your readers to share your posts, don't you? :)

Have technical support issues? Please leave them in the forum: http://wordpress.org/tags/sociable?forum_id=10 Also use the forum for ideas, feedback, suggestions. We'll try to check the forum every day.

What happened to the old icons? You can still use them in the new version, but they're not the default style anymore.

Sociable finds its home outside of the WordPress environment on Blogplay.com-

*** Sociable 4.0.2 ***

Recent Updates

• Changed the old motto "share and enjoy" for "Be Sociable, Share" much more attractive. Of cours you can customize it to whatever you want.
• Complete re-write to increase efficiency and speed of the plugin

Recently Added Sites

• Posterous
• Sphinn
• Tumblr

Recently Deleted Sites

• Mixx.com, recently acquired, doesn't support share functions anymore
• Netvibes stopped sharing
• Slashdot: New bookmark creation is no longer supported
• And we deleted a bunch of others that were really not used that much

Special Thanks

Sociable plugin wouldn't be what it is today if it weren't for these people that helped us along the way: * Thanks to WPzoom for letting us to use their awesome icons * Also special thanks to Webtreats etc for allowing us to use their great icons

Download, Upgrading, Installation:

Upgrade

1. First deactivate Sociable
2. Remove the sociable directory

Install

1. Unzip the sociable.zip file.
2. Upload the the sociable folder (not just the files in it!) to your wp-contents/plugins folder. If you're using FTP, use 'binary' mode.

Activate

1. In your WordPress administration, go to the Plugins page
2. Activate the Sociable plugin and a subpage for Sociable will appear in your Options menu.

If you find any bugs or have any ideas, please mail me.

Advanced Users

For advanced use of the plugin, see the Sociable page on Blogplay

What happened to the old icons?

You can still use them. It's just they're not the default anymore.

I want to reach you, but not for a technical question

Please send us an email to sociable [ at ] startups.com

1. 

   The Sociable backend, easily select sites and drag & drop to change the order of appearance.

2. 

   Sociable with its new default styling.

3. 

   Pick the style you want

4. 

   Or you can pick your own style

4.0.2

Fix IIS 6.0 and PHP 5.3.x

4.0.1

• Changed the old motto "share and enjoy" for "Be Sociable, Share" much more attractive. Of cours you can customize it to whatever you want.
• Complete re-write to increase efficiency and speed of the plugin
• Updated it for up to Wordpress version 3.2.1

3.5.2

• Added new services MOB, 豆瓣, 豆瓣九点, QQ书签, LaTafanera, SheToldMe, viadeo FR, Diggita, Design Float
• Removed ID properties from sociable anchor tags (share links)
• FIXED: Having a custom image directory now disables sprite usage, and the icons of services are displayed on sociable configuration page.

3.5.1

• Fixed the xhtml validation issues
• 'target=blank' (open link in new window) issue solved
• Sprites can now be disabled, allowing for custom icons
• Sprites have been disabled for RSS
• You can now deactivate the blogplay widget from your wordpress dashboard

3.5.0

• The icons now load in a CSS Sprites, allowing for faster download times.
• These services have been discontinued: BlogMeme FR, BlogMeme SP, co.mments, DesignFloat.com, PPNow.net, Symbaloo.com.
• You can now add links to your browser favorites.
• iFrames added for services that support them.
• You can know unselect the transparency effect on the sociable icons.

3.4.4

• Another fix for the sociableoff dilemma's, no backwards compatibility unfortunately, so disable sociable again on pages where you want to disable it.

3.4.3

• Fixed the bug mentioned here and here that made it impossible to disable Sociable on a per post/page basis (for real, now).

3.4.2

• Added a site specific id to each links anchor tag.
• Fixed the bug mentioned here and here that made it impossible to disable Sociable on a per post/page basis.
• "Reintroduced" TwitThis as Twitter.

3.4.1

• Fixed the Sphinn submit link.

3.4

• Added the option to add a site to Sociable through a filter, read How to add a site to Sociable.

3.3.8

• Fixed the option to disable Sociable on a per post / page basis.

3.3.7

• More bugfixery.

3.3.6

• Reverted plugin URL fix because of too many people on old WordPress installations complaining. (Upgrade, people, upgrade!)
• Added PHPDoc throughout the plugins code.

3.3.5

• Added a Hyves button.
• Fixed MSN Reporter button.

3.3.4

• Fixed RSS.

3.3.3

• Brought back Tumblr
• Updated PDF link
• Added Posterous
• Smushed all images using Smush.it, reducing the total image file size with 31.72 KB (42.03%)!
• Removed pre - 2.6 compatibility code

3.3.1

• Added new option to use pure text links, instead of image links.
• Fixed small issue with using target=blank links and the new awe.sm options.
• Allowed for usage without an awe.sm API key, as awe.sm falls back to "default" awe.sm shortlinks.
• Code cleanup for more efficiency in the backend on saving options.
• General code cleanup.
• Moved to the new default Changelog markup.

3.3

• Added awe.sm integration and some sites.

3.2.3

• Removed the last bit of non jQuery javascript.
• Improved styling and visual feedback when selecting a site.

3.2.2

• Moved style loading to admin_print_styles and scripts to admin_print_scripts.

3.2.1

• Fixed a bug with printing styles in 2.8 beta.

3.2

This is a MAJOR update to Sociable. Major Thanks to Jean-Paul of iPhoneclub for all his work in looking up all the sites. The full list of changes:

• Restored sociable-admin.js, as it got accidentally removed.
• Added class="sociablefirst" to the first site in the list and class="sociablelast" to the last one.
• Added:
  • An RSS button, which links to your sites RSS feed
  • Printfriendly.com for both printing and creating a PDF, replacing the original "Print" function, which didn't work from RSS
  • Current
  • FriendFeed
  • MSN Reporter.nl
  • FS Daily
  • Hello TXT
• Removed the following sites that were no longer working or active:
  • BlinkBits
  • Blogmemes.cn, .net, .jp
  • Blogsvine
  • Book.mark.hu
  • Bumpzee
  • Del.irio.us
  • Feed Me Links
  • Furl (replaced by Diigo)
  • GeenRedactie
  • Kick.ie
  • Leonaut
  • Magnolia
  • Plug IM
  • Pownce
  • Salesmarks
  • Scuttle
  • Shadows
  • Smarking
  • Spurl
  • Taggly
  • Tailrank
  • Tumblr (due to the change to a POST API, which we, unfortunately, can't support with Sociable)
• Updated the following sites to include the excerpt when submitting:
  • Connotea
  • Delicious
  • Digg
  • Ekudos
  • Google Bookmarks
  • NuJij
  • Ping.fm
• Otherwise updated:
  • Google Bookmarks (new icon)
  • Fleck (New URL)
  • Rec6 (new URL)

3.1.1

• Fixed bug with stylesheet introduced in 3.1.

3.1

• Converted all images to PNG.
• Cleaned up usage of javascript in the backend and switched to the jquery library that comes with WordPress.
• Allowed for usage of an external image directory.
• Removed pre 2.6 compatibility fixes.

3.0.6

• Fixed xhtml bug in Netvibes integration.
• Added Bitacoras.

3.0.5

• Added Identi.ca.
• Fixed a bug in Yoast Posts widget.

3.0.4

• Added Netvibes.

3.0.3

• Security enhancements, thx to Mark Jaquith.

3.0.2

• Fixed CSS bug introduced in 3.0.

3.0.1

• Removed some other, now obsolete, code, reducing the code size by another 4KB.

3.0

• Fixed IE bug in admin.
• Cleaned up Admin Area and changed support messages.
• Removed directory checking for all images (speeds up incredibly).
• Made display: inline !important to prevent vertical icon display.
• Updated Wykop icon.

2.9.15

• Added a fallback for strip_shortcodes to maintain backwards compatibility with WordPress 2.3 and below.

2.9.14

• Made sure there are no tags or shortcodes in the excerpt.
• Added ping.fm.
• Removed indiagram (shut down).

2.9.13

• Changed Facebook link from sharer.php (meant for a popup window) to share.php (which has the actual menu on it etc.).

2.9.12

• Added Tip'd.

2.9.11

• Added settings link and Ozh admin menu icon.

2.9.10

• Fixes issue with excerpt not being urlencoded.

2.9.9

• Fixes for custom fields issues.

2.9.8

• Fixes for WP 2.7.

2.9.6

• Added Symbaloo and Tumblr.

2.9.5

• Fixed Fark & Propeller links.
• Added missing i18n strings.
• Added Yahoo Buzz.

2.9.4

• Removed PopCurrent and Rawsugar as they no longer exist.
• Renamed BlueDot to Faves.

2.9.3

• Added Leonaut & MySpace.
• Fixed plugin description.
• Added option to disable Sociable on a per post basis.
• Added option to display sociable on tag pages.
• Added extra security to config page.
• Fixed print button.
• Fixed Twitter functionality.

2.9.2

• Added Swedish and Chinese localisations, thx to Mikael Jorhult and Hugo Chen.

2.9.1

• Fixed bug where jQuery UI would be loaded twice.

2.9

• Removed Tool-Man in favor of jQuery, thx to Martin Joosse.

2.8.4

• General bugfixes.

2.8.3

• Added wikio.it, upnews.it, muti.co.za.
• Made LinkedIn work even better.
• Made opening in a new window optional.

2.8.2

• Now adds icons to feeds with excerpts too.
• Added LinkedIn.

2.8.1

• Fixed some small issues.
• Made sure tagline shows up again.

2.8

• Added option to show bookmark icons in feed.
• Added Ratimarks.
• Fixed xhtml compliance.
• Fixed blue dot bug.

2.6.9

• Fixed WP 2.6 compatibility.

2.6.8

• Updated inline documentation.

2.6.7

• Renamed Sk*rt to Kirtsy.
• Added designfloat.
• Fixed description.

2.5.4

• Added HealthRanker, N4G, Meneame, BarraPunto, Laaik.it and E-mail option.

2.5.3

• Added Global Grind, Salesmarks, Webnews.de, Xerpi, Yigg.

2.5.2

• Added NuJIJ, eKudos, Sk-rt, Socialogs and MisterWong.de.

2.5.1

• Swapped Netscape for Propeller.

Special thanks to Robert Harm for coming up with loads of nice ideas.