Tweete ( m.tweete.net): Tweete is a light weight (14KB) mobile client that should work well on old or low tech phones and/or slow networks. Tweete manages to include a lot of features like quick action icons for direct messaging, @replies, “favoriting” and “un-favoriting”, “following” and “unfollowing” Twitter users.
Friend or Follow ( friendorfollow.com): It compares the people you’re following with those who are following you.
Qwitter ( useqwitter.com): It lets you know who stopped following you, and what post sent them over the ledge.
Twitter2Go ( twitter2go.com): It provides a WAP or xHTML-MP interface that works on Palm, Pocket PC, BlackBerry, and almost any other mobile phone or PDA device.
iTweet 2 ( itweet.net): It is the best interface for using Twitter on the iPhone or the Web! Built-in autorefresh, search and hashtags.