A lot depends on your image size. For web video, shrinking it down to something like 320x240 will make a huge difference.
QuickTime is MPEG-4, as is DIVX, and this format will produce the best image with the smallest file size. Playing with different audio codecs will also allow smaller files, mono vs stereo, etc.
With decent quality stereo sound, and 640x480 image, MPEG-4 should give you about 30MB per 5 min, give or take. Bumping that up for higher motion detection or spacial quality can double or tripple the size. DVD quality video at 640x480 with stereo sound will run you around 20MB per min with high-quality motion settings. It can vary quite a bit when comparing video with little motion to video with a lot of motion.