No 2. Twit-Twoo

This allows you to update your twitter status right from your blog’s sidebar. Twit-Twoo is simple to install and use, AJAX makes it all look so easy.

Here is the download link.

No 1. Twitter tools

This plugin integrates you twitter account with your WordPress-blog, allowing you to pull tweets into your blog and create new tweets on blog posts. It also allows you to create new tweets from within WordPress.

Here is the download link.