I just found this free downloadable sequencer called Rubber Duck based on the TB-303 but way weirder. It was made way back in 1996. It's very fun to play with and can be downloaded here. I made some crazy sounds and scared the dog a little.
Also check out Drum Station, a free download from the same site which is an 8 track sequencer / drum machine pre-loaded with classic drum sounds, or add your own.
