I just finished building a jQuery-based Twitter plugin - http://www.pay4tweet.com/pay4tweet_plugin.php . I couldn't find one that allowed for all the customizations I wanted. The problem is that now it's pretty complex. If anyone can find any problems with it (or the demo page for that matter), please let me know.
Also, although, I'm not an open source guru, I'd like to eventually make it open once I'm comfortable with the stability of the starting code. Any suggestions, or references, on where to begin that process? Or, are there any other 3rd party open source Twitter development projects that people are aware of? -Mo