You can now try the Nouveau free software nVidia video drivers from Debian experimental.
Read it here
For the status of the drivers with your particular card, please see upstreams compatibility matrix. My experience has been positive; I have been using them for about two months on my dual-head 8600GT (NV50) setup with only a few small issues and a generally superior Gnometris experience.
* If you find bugs (unrelated to the packaging), please report the problem upstream and not in the Debian bug tracker.
* At request of upstream, we are not providing 3D support. Please do not ask for it, as a wontfix tag often offends.
* Bonus points are awarded for removing the non-free nVidia driver; although installation of xserver-xorg-video-nouveau will remove nvidia-glx, purging nvidia-kernel-common and nvidia-kernel-source should remove all the module-assistant generated kernel modules. rms would be proud.