Checks Twitter usernames mentioned in the content and in the comments (eg. @tquizzle) with the Twitter service to see if that user is indeed a Twitter
Checks Twitter usernames mentioned in posts, pages and in the comments (eg. @tquizzle) with the Twitter service to see if that user is indeed a Twitter user, then converts that user's Twitter name to a link to the mentioned user's Twitter profile page (eg.@tquizzle).
Important: As this plugin converts usernames on the fly (whenever and everytime somebody views posts, pages, or comments), and checks Twitter for every username (to ensure it's valid), I strongly recommend using a caching plugin such as WP Super Cache. It will not only lessen the load on Twitter's servers, but obviously speed up page loads in the process.