YouTube is available on Roku, and works excellently.

I have all the users that upload old Formula 1, so I can watch old races whenever I want.

Democracy Now also has it's own Roku channel, as do many many other things like Ted that you might not have thought of. It's worth spending some time on Google searching this stuff out.

I'd say I spend more time watching YouTube, NetFlix and HULU+ on the Roku than any other consumption mechanism.

Local news on OTA HD follows behind.

One slightly sad note, I only have the base Roku, and it's quite slow (maybe buffering), so my 2 year old is now utterly tolerant of loading bars, and will watch the loading bar, since she knows that content will follow. Her absolutely favorite thing on TV, though she doesn't watch much (seriously), is the mime segment on Nihongo Quick Lesson, NHK's little Japanese-lessons show that runs about 2:15pm, right after her lunch. I guess really, it's not much different to me as a kid waiting for the TV to warm up and show a picture...

As a side note to this, the Apple TV works very, very well for streaming from your iTunes movie library. I'm in the slow-ish process of converting my entire DVD library over to video files that iTunes likes for this purpose.