GraphicEdit

This plug-in allows you to create and place a GitHub css3 badge to your webpage on wordpress. With the help of this plug-in you create a css3 badge for your users or followers helping them to follow your GitHub account. This plug-in is very useful for GitHub users, for users who would like to promote his/her GitHub on WordPress.
Links: <a href="http://graphicedit.com/" rel="nofollow ugc">Author Homepage</a>

GitHub Badge

This plug-in allows you to create and place a GitHub css3 badge to your webpage on wordpress. With the help of this plug-in you create a css3 badge fo …

Tanmoy

The normal Text widget allows you to insert arbitrary Text and/or HTML code. 
This allows that too, but also parses any inserted Shortcode and PHP code and executes smoothly.
All Shortcode must be enclosed in the standard [ and ] tags for it to be 
recognized. 
All PHP code must be enclosed in the standard tags for it to be 
recognized.

WP Sidebar Essential

Like the Text widget, but also allows working PHP code and shortcode to be inserted.

GitHub Badge vs WP Sidebar Essential