Use H.264. Go into QuickTime Pro Player, size the video's window to as small of a size as you can live with. Export "Movie to Quicktime", and as an H.264.
In the Video settings, set the keyframe/rate stuff all set to "Automatic", turn on frame reordering, select multi-pass processing. In the Video Size settings, use Current. For regular computer playback, leave at full screen size. For web viewing, I shrink to a width of 450. The Compressor Quality slider should be full rez for full size viewing on a computer screen, and Medium or just below if going to the web.
For sound use ACC, 24.000, 48 bit rate, VBR, stereo, it'll sound great.
You'll then have great full size or web size files for playback at good quality. If going out to the web, make sure "Internet Streaming" is set to "Fast Start".