Tweetlater – Schedule tweets, bulk upload tweets, track keywords, send welcome DMs, URL shortening, auto following, more.

appTracks: Web
appTags: auto following, direct messages, keywords, schedule tweets, tracking, url shortening

Twurl – Shortens URLs for your tweets.

appTracks: Web
appTags: url shortening

Tweetburner – Track the links you share on Twitter and FriendFeed.

appTracks: Web
appTags: friendfeed, link, tracking, url shortening