Canary – open source Twitter client for Macs.

TwitDiff – email/RSS notifications of unfollows.

Twidentify – search engine that sorts results by people who get retweeted the most.

Twitemperature – Find out how hot you are. How does it work it all out? “We poll your last several hundred tweets and score what you’re saying against what everyone else is saying in current hot conversations on Twitter and elsewhere.”

Twitter Venn – enter 2 or 3 search terms and see results displayed in a pretty Venn.

Destroy Twitter – Adobe AIR Twitter client.

Twitlonger – Write more than 140 characters, describes itself as Twitpic for text. DM @stuartgibson for  an invite to the Beta.

twtcard – e-cards for Twitter.

Mr Tweet – get recommendations on who you should follow (based on your extended Twitter network) from Mr Tweet (who is an owl btw).

Twits Near Me – displays (an automatically refreshes) recent Tweets from people near you.