An experimental firmware with support for VP6 codecs, VP8, MJPEG and Ogg Theora
DOM, one of the active members on the developments of the Raspberry, just released a new firmware for the Raspberry Pi with a hardware video codecs VP6 support, VP8, MJPEG and Ogg Theora. The Ogg Vorbis audio codec is also part. The acceleration will be done not by the GPU (as is the case for the H264, VC1 and MPEG-2) but by the CPU. It seems to limit the videos to SD or 720 p.
If you are a true geek, You can install it you even. All instructions are There. Get ready to the compilation galore ! But it leaves a good hope for better support for some codecs in XBMC coming soon.