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The Google Analytics for WordPress plugin allows you to track your blog easily and with lots of metadata.

Check out the Google Analytics for WordPress video:

Full list of features:

• Simple installation through integration with Google Analytics API: authenticate, select the site you want to track and you're done.
• This plugin uses the asynchronous Google Analytics tracking code, the fastest and most reliable tracking code Google Analytics offers.
• Option to manually place the tracking code in another location.
• Automatic Google Analytics site speed tracking.
• Outbound link & downloads tracking.
  • Configurable options to track outbound links either as pageviews.
  • Option to track just downloads as pageviews in Google Analytics.
• Allows usage of custom variables in Google Analytics to track meta data on pages. Support for the following custom variables:
  • Author
  • Single category and / or multiple categories
  • Post type (especially useful if you use custom post types)
  • Logged in users
  • Publication Year
  • Tags
• Possibility to ignore any user level and up, so all editors and higher for instance.
• Easily connect your Google AdSense and Google Analytics accounts.
• Option to tag links with Google Analytics campaign tracking, with the option to use hashes (#).
• Option anonymize IP's, for use in countries like Germany.
• Full debug mode, including Firebug lite and ga_debug.js for debugging Google Analytics issues.
• Allow local hosting of ga.js file.
• Tracking of search engines not included in Google Analytics default tracking.
• Tracking of login and registration forms.

Other interesting stuff:

• Check out the other WordPress Plugins by the same author.
• Want to increase traffic to your WordPress blog? Check out the WordPress SEO Guide!
• Check out the authors WordPress Hosting experience. Good hosting is hard to come by, but it doesn't have to be expensive, Joost tells you why!