+++ Graeme Russ [2012-10-03 09:10 +1000]:
Many platforms have some binary blobs which you can download to get video decoders and 3D graphics. The ARM cores are getting so fast today that you can probably decode hi-res videos using FFMPEG...
Yes, this is what disappoints me. This is not promising at all:
http://en.wikipedia.org/wiki/Graphics_hardware_and_FOSS#ARM
Mali (ARM), PowerVR (Imagination Technologies) and VideoCore (Broadcom) are the main 3D graphics cores for ARM based chips. None have (and none of the vendors have any interest in providing) FLOSS drivers.
Your best bet for free video drivers is probably Mali at the moment, as that's the furthest-forward reverse-engineering project (SFAIK). But Snapdragon (Qualcomm) is also worth considering as Freedreno has also made useful progress. There are at least 5 different graphics cores available, and 3 or 4 of them have RE projects to free them up, but it'll be a while before any are in useful shape.
If you have any relevant expertise (or would like to aquire some) you will be exceedingly welcome to help out.
http://limadriver.org/ http://freedreno.github.com/
Wookey