MPEG 4 rocks!! Oh, well I'm an MPEG fanatic (mpegif.org woohoo!) I would say MPEG 4, for video and audio.
Here's the setting I use for my internet videos (you can see the quality here
http://homepage.mac.com/directorlca/...Theater30.html )
This is just what I use, but play with your own too
320x240
29.97
bitrate: 368kbps
audio 48khz (mpeg4 audio sounds like CD audio basically)
2 channel, 128kpbs
so with those settings a video that's 1.5 minutes would be roughly 5MB. for 16x9 video, just change the res to 320x180 or whatever floats your boat. So. . . that's just what I use, you can increase the bitrate for higher qualiy, but that makes the files bigger too . . hope that helps!!