Well, I'm getting round to uploading my video to youtube. After the tutorial with Simon, he suggested looking at the proper sizes that youtube uses, to minimize the loss of quality youtube causes with compressing. I found a useful link - http://www.lafcpug.org/Tutorials/basic_you_tube.html
It tells you about what codec youtube uses, and what size. To get the most from youtube, export your videos with the correct size and the appropriate codecs!
And here - http://www.vimeo.com/help/compression - is the same for vimeo. Vimeo's a little less mainstream than youtube, which is good because you get a hell of a lot less shit on there.
Finally - http://www.google.com/support/forum/p/blogger/thread?tid=53c9daac1f8dde71&hl=en - this link tells you how to correctly embed videos on blogger with regards to the sizing. It turns out that copying the youtube embed code will produce a video that's too wide for your blog, so this link tells you how to sort that out.