There are a couple that I've listed below, scan through them and see what you can find. They aren't in any particular order. Just a list of free tools ready to be utilized. If your are already an avid affiliate marketer, I would like to hear of your success on Twitter. Post a comment!
Qwitter – a tool that notifies users someone unfollows you.
TweetWheel – a tool that identify which of your Twitter friends follow each other.
Twitter Charts – graphs of when individual Twitter user is most active.
twInfluence – ranks the influence of a particular Twitter user

TwitterGrader – The most popular tool to grade Twitter users
TwitterSheep – a tool that can create a tag cloud of words taken from the bios of a given Twitter user’s followers.
TwitterCounter – Provides stats on a given Twitter user and lets you compare that user to two others.
Twellow – The webs most popular Twitter directory.
TweetBoards – we now can compare Twitter users side-by-side.
TweetStats – a tool that displays the more popular stats a Twitter user
TwitterMeter –a keyword meter that creates graphs from Twitter public timeline
TwitterLocal – a desktop application that finds Twitter users within a given city or zip code.
Mr. Tweet – a great tool that provides statistics on your Twitter usage
Localtweeps – Find local tweets
Twits Like Me – a tool that suggests Twitter users that are in your niche











