Metropho.rs is a geographic metaphor map that plots "X is the Y of Z" tweets by putting the "Y" label on the "X" location. Some nice coverage by the Atlantic Cities blog here. [more inside]
Twittov generates nonsense from your Twitter history using Markov chains. Note: Your tweets must be public for it to work. I posted this as a python script a year ago, but it's totally rewritten for the new Twitter API and has a Django/jQuery interface.