http://kookybot.org/
That's my IRC bot which uses a Markovian style algorithm. It sits in hundreds of IRC channels learning everything it hears, then generates replies based on that. Some of the best quotes are randomised on the front page (refresh to see more). You can find more at:
http://quotes.kookybot.org/top
Everything there is generated from its knowledge - it is not simply repeating back sentences it has heard. The database is 4.6 GB, almost 70 million rows.