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.

Luka Petrovic

Adds Favicon to every external link inside posts. It uses external favicon service that you can alter. You can alse choose position of icon and limit change with css selector.

Favicon on external URLs

Adds Favicon to every external link inside posts. It uses external favicon service that you can alter. You can alse choose position of icon and limit  …

Karedas Favicons vs Favicon on external URLs