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

Prasanna SP

silverks

Twiget Twitter Widget lets you display your latest twitter status updates in any of the widgetized areas. Just add the Twiget Twitter Widget to your sidebar or any of the widget areas and enter your twitter username. It will display your latest tweets along with a follow @username button to make it easier for people to follow you! You can configure widget title, twitter username, number of tweets to display, link target etc, in the widget configuration.
Features:
<ul>
<li>Twitter API 1.1 support</li>
<li>Twitter requests caching with auto-optimised duration for performance</li>
<li>AJAX-based so your site’s load time is not affected by Twitter’s server</li>
<li>Multiple instances of widget</li>
<li>Option to change widget title</li>
<li>Option to change number of tweets to display</li>
<li>Option to show followers count, profile picture, and Twitter bio</li>
<li>Option to show twitter client used. Eg: via Twitter for Android</li>
<li>Option to open links in a new window</li>
<li>Option to hide @replies</li>
<li>Linkified @usernames and #hashtags</li>
</ul>
Twiget is developed by <a href="http://www.khairul-syahir.com/" rel="nofollow ugc">Syahir Hakim</a> of <a href="http://www.graphene-theme.com/" rel="nofollow ugc">Graphene Theme</a> and <a href="http://www.prasannasp.net/" rel="nofollow ugc">Prasanna SP</a>.
Translation: If you want to translate this plugin to your language, please find the twiget.pot file in /languages/ folder.
Demo: See demo of this plugin <a href="http://demo.prasannasp.net/" rel="nofollow ugc">here</a>. It is the second item in the sidebar.
Support: Please post your support questions at Twiget Twitter Widget plugin <a href="http://forum.prasannasp.net/forum/plugin-support/twiget/" rel="nofollow ugc">support forum</a>.
Visit <a href="http://www.prasannasp.net/wordpress-plugins/" rel="nofollow ugc">this page</a> for more WordPress Plugins by the developer.
This plugin uses Abraham’s [twitteroauth library] (https://github.com/abraham/twitteroauth‎/).

Twiget Twitter Widget

A widget to display the latest Twitter status updates.

WG Twitter Widget vs Twiget Twitter Widget