This plugin is used to convert the following formats:
* @username -> http://twitter.com/username
* @username/listname -> http://twitter.com/username/listname
* #hashtag -> http://search.twitter.com/search?q=%23hashtag
It comes with some options to configure, like use nofollow attribute, open on a new page and choose where you want the links to be replaced.
Requires WordPress Version: 2.9 or higher