Add 16×16 favicon after all the links in your posts. 
The favicon’s tag has a ‘favlink’ class so you can CSS it as you wish.

Karedas Favicons

Adds corresponding favicon from Google Shared Stuff after every links in your posts.

yoshitech

Parses posts for external links and puts their favicon next to them. It uses http://g.etfv.co/ service for getting the url favicon. 
You can see the demo at http://kupimito.com/
Misc
<ul>
<li><a href="http://www.kupimito.com" rel="nofollow ugc">Plugin website</a></li>
<li><a href="https://www.paypal.com/cgi-bin/webscr?cmd=_s-xclick&hosted_button_id=SPY83T4ZJM26Y" rel="nofollow ugc">Donate</a></li>
</ul>
<h3>Arbitrary section 1</h3>

FavParser

Parses posts for external links and puts their favicon next to them. It uses http://g.etfv.co/ service for getting the url favicon.

Karedas Favicons vs FavParser