TP – TweetPress plugin by ouyx gives you all the tools you need to integrate your wordpress and twitter… based on the “Simple Twitter Connect” plugin, but highly customizable.
Allow your visitors to comment using their twitter ids
Adds a tweet button to your posts, so your visitors can share your content.
Allow your blog users to sign in with their twitter ids. one click signin!
Automatically publish new posts to a twitter account.
Easily customizable by theme authors.
Add a follow button to your blog
Download and info: http://wordpress.org/extend/plugins/tp/