No 4. TwitterLinker

This plugin adds an extra field of twitter username in your comments form. So, a “follow me” link is displayed along with the user’s comment. The “follow me” link is very much configurable.

Here is the download link.

No 3. TweetMeme Button

Used by some of the biggest websites like CNET.com, Wired and Break.com, this plugin allows easy retweeting of you blog posts. It also gives you the ability to control the length of the tweets. Furthermore, it also features live count of the retweets of your page.

Here is a tutorial for it:

[youtube]http://www.youtube.com/watch?v=wL-OUqfwd64[/youtube]

Here is the download link.