Aaron Plattner of NVIDIA requested and then had established a VDPAU mailing list under the FreeDesktop.org umbrella. From Bug 44470, "It would be nice to have a list for discussing changes to libvdpau and vdpauinfo. It might also be useful for discussion of VDPAU implementation in Mesa/Gallium, if those guys want to use it for that."
VDPAU up to this point hasn't seen too many radical changes, so it also raises the question whether NVIDIA has something new on the horizon. Since 2008 there's been PureVideo implemented via VDPAU yet in 2012 is when NVIDIA's seeking to establish a community list for the work. Will something interesting be coming for video decoding with Kepler or its successor to warrant a fundamental shift at this point for VDPAU?
This mailing list was also created at a time when a new list for an open-source driver wasn't even created earlier this year on the basis of "Most drivers (including AMD) seem to get along just fine without a project-specific mailing list, and we have no end of now-dead lists on fd.o." The new VDPAU mailing list meanwhile has zero postings at the moment.
The VDPAU support within NVIDIA's binary Linux driver for the GeForce 8 series has been excellent since its launch. The support continues to be refined with new binary driver releases, but overall the video decode implementation has seen little negative criticism. The VDPAU results speak for themselves, it does a phenomenal job of offloading doing video acceleration on the GPU rather than CPU.
Outside of NVIDIA, there is the supposed VDPAU video decode support within S3 Graphics' Linux driver. The Gallium3D implementation in Mesa also has a VDPAU state tracker to expose this video acceleration API on Radeon and GeForce (via Nouveau) hardware. However, at this point the work is being done via GPU shaders.
AMD hasn't yet opened up any Unified Video Decider documentation/code (UVD; their on-chip video decode/encode engine) and the Nouveau developers are left to reverse-engineer NVIDIA's video engine. Intel supports open-source video decode/encode with their latest hardware under Linux, but they are content at this point in supporting VA-API with no expressed signs of possibly adding in VDPAU capabilities.
On the application side, VDPAU is widely supported by all major multimedia Linux projects (MythTV, VLC, XBMC, etc). VDPAU is also the video API of choice for Adobe's Linux Flash Player.
That's about the state of NVIDIA VDPAU as of early 2012 for those not up to speed on this Linux video acceleration API.
Those wanting to subscribe to the VDPAU list can find it at lists.freedesktop.org.