Best codec for web video?

A completely non P5 question, what is the best way to encode an SD video clip for web viewing?
What is the best codec to use?

For Youtube and Blip.tv - .mp4/h.264 quality 65%
For flash players - .flv
If you want to place an encripted video that only a hacker can steal:
www.videovista.it

I encode .MP4 for maximum compatibility with devices.

I've used H264 for Youtube/Vimeo as well. I honestly can't tell you about codecs for other purposes.

Thanks Guys. Just not sure what's best myself.

For YouTube I have had best luck with .mp4 or an .Mov/h264.

intelaced V progressive for web what's best?

Progressive, because mostly will be viewed on computers that dont manage interlaced.