Indeo video 5.10 as far as I know is on every PC. The compression is reasonable. DivX and XviD are probably the two better options and are readily available. Or maybe create 2 with different file extensions, eg. mpg and avi, so that they will have an option on which one to choose from. Or render the demo reel out to 720x486 (30fps for NTSC) and convert the avi to a DVD disc. That way it will play in any DVD player.
This link might be helpful
http://www.pixar.com/companyinfo/jobs/howto.html
Thanks to freddyhard for the info.