I've been doing alot of online content lately and it seems that most people are relying on flash video for HD content.
I don't know the specifics in terms of settings, bc I haven't been doing the compression myself - but you can see some of the videos in the links in my sig below.
I know the company I'm working with was using Squeeze at one point to compress the shows, and they looked MUCH better...they switched compression software recently for other reasons, and the quality has suffered a bit.
Your other option would be H.264 - but then you won't have nearly as much compatability (i think) with PC users.
Then again...I might have no idea what I'm talking about.