Marco Buttarini

wg-twitter-widget is THE widget to show twitter status in wordpress sidebar. 
Developed starting from the existing widget of Sarah Isaacson, * using the example widget of Justin Tadlock

WG Twitter Widget

Twitter Widget Highly configurable, with image and last twit of users

Curtiss Grymala

Adds an available widget to list various social media profiles. The following social media sites are included by default:
<ul>
<li>Facebook</li>
<li>Twitter</li>
<li>YouTube</li>
<li>LinkedIn</li>
<li>Google+</li>
<li>FriendFeed</li>
<li>Flickr</li>
</ul>
This plugin also includes a filter hook allowing you to extend the available services.
By default, this plugin outputs an unordered list (ul) with a class of <code>social-icons-list</code>. Each service is output as a list item (li) with the service name used as the HTML class attribute. Filters are available to allow you to change those HTML elements.

Social Icons Widget

A developer-friendly plugin that allows you to add a widget with links to various social media profiles.

WG Twitter Widget vs Social Icons Widget