Here is a link to some FB plugins, but they let users share your content on their Facebook. I just use AddThis button that does all the bookmarking sites.
http://tomuse.com/wordpress-facebook-plugin/
But if you mean icons to link to your FB Fanpage or Twitter page, just use your fave image, and add it to a TEXT widget (in the Appearance > Widgets page) in the footer (or sidebar if your theme won’t accept widgets in the footer), then add the link to the images to each of your pages.
I would download the image, then upload it to tinypic.com or your own site. Then make a note of the plain URL.
Here’s the code to make images links (remove “blank” if you don’t want them to open in a new window):
<a
target="_blank"
href="http://www.thedomainyouwanttolinkto.com"><img
src="http://www.imageurl.com/theimagetitle.jpg"
border="0"></a>
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