nouveau, the project for creating a free 3D linux driver for nvidia cards, recently got first support for real 3D applications with gallium on some NV4X cards (see Nouveau Companion 36). Today I got it working on a friends machine.
It’s really impressive, but keep in mind this is still in early and heavy development, and not considered ready for general use.
Meanwhile, OpenTheBlob.com is a site petitioning NVIDIA to follow AMD’s lead and open source a 3D driver of their own:
While we are grateful that your company provides one of the best closed-source graphics drivers for Linux, it is not without its problems and prevents many users from having a truly free software platform. You have shown an open-source passion in the past when dropping the nforce-net binary blob in favor of the community-spawned forcedeth driver for Ethernet support on your motherboard chipsets.
Interested parties can also sign the petition themselves (as of this writing, there are 7894 signatures). Furthermore, there’s contact information and a sample letter for writing NVIDIA’s various customers about open support (thanks Phoronix).