Where can I find a collection of sample videos that use various container formats / codecs / bitrates / resolutions to use as test data?

Question

I'd like to get hold of a wide range of videos to use as test data. I'd ideally need Flash, Quicktime and Windows Media containers with video content at various bitrates and resolutions.

Before I set out gathering or creating such a collection myself, does anyone know if a similar repository of sample video data already exists? Perhaps a media player or stream server project maintains something like this?