If you've got an iPhone, iPod Touch, or G1, you're in luck. I'm guess it'll work with the Pre. Probably the Blackberries. Here goes.
Point your mobile browser here: NBC Mobile. You can watch many videos including full episodes. It was a sweet discovery and I'm glad to be sharing it with you.
For other mobile sites that offer videos for your iPhone or G1, go to Onxo Mobile Tips.
Note: I don't know if this works for all smartphones. I assume this will work with the Pre because its browser is based on Webkit, the same used in the iPhone and G1. But I think it has more to do with H.264 video support.