Disclaimer - Production Nerd Alert: I just purchased the Canon T2i, and shot some sample footage of my son finding snails in a nearby pond. I used the Canon 18-55 lens, and shot the video at 1080p 24 fps. I used the auto movie settings, and used the Zoom H4n for audio at 44.1khz.
For post, I used MPEG Streamclip to convert the file to 960x720 using the DVCPRO HD 720p compressor, and edited in Final Cut Pro. I then used Compressor to export for Vimeo using H.264 compression with AAC audio.
I am really impressed with the results, and had to subscribe to Vimeo who I feel have the best support for online HD video.