Maarten Lankhorst, commonly working on the Nouveau driver, has published four patches for the VDPAU state tracker. The one worth mentioning is the support for MPEG4 Part 2. However, before getting too excited, it's just the support patch and no Gallium3D driver/decoder implements the support yet. Hopefully that will soon change.
MPEG4 Part 2 support in Gallium3D's VDPAU implementation will be useful since this standard is commonly used by codecs such as DivX and Xvid. MPEG1 and MPEG2 are the other formats currently supported by Gallium3D's VDPAU state tracker.
Among the video formats that can be decoded by NVIDIA's Video Decode and Presentation API for Unix are MPEG1, MPEG2, H.264 / AVC, VC-1, MPEG4 Part 2 / ASP, DivX4, and DivX5 (there's a total of 21 different VDPAU decoder profiles right now).
Here is the mailing list patch that implements the MPEG4 Part 2 support within the VDPAU state tracker.