Twitter's Dirty Bird
Twitter works because of its simplicity. The only complex part of it is how the individual uses it - meeting people, breaking news, sharing information, or droning on about your grey, empty life and the insignificant events that comprise it.
Of course, the fact Twitter has a wellspring of 3rd party applications that are actually useful is a leg up, particularly interfaces like Tweetdeck, Twhirl, and Digsby. But I also have a roll of quarters in my pocket for the myriad of apps that exist solely for entertainment or ego's sake.
Here's a pretty sweet list of Twitter tools guaranteed to suck you in like a gaggle of geese into jet turbine of unproductivity.
From the list, my new favorite: Cursebird (actually found this first via Geo. Parker over at AdScam). Cursebird's a little Twitter search engine that scours a user's tweets for instances in which they've bandied about an expletive - from the tame to the "Queen Mother of all dirty words." Then, it ranks the user on a cuss-scale of 1-100. I was impressed that, out of 4 million-odd users, I ranked a solid 13,969 with a score of 96.
Probably my best score since finger-painting was graded.