There are these packages in unstable which you probably want to install:

• xserver-xorg-video-nouveau The 2D DDX
• libgl1-mesa-dri The 3D drivers

Other packages will automatically be installed as dependencies, such as

• libdrm2
• libdrm-nouveau2

Newer versions of these packages are occasionally available in Debian's experimental repository.

If you run into problems, you may want to install various -dbg packages to debug them:

• xserver-xorg-video-nouveau-dbg
• libgl1-mesa-dri-dbg
• libgl1-mesa-glx-dbg
• libdrm-nouveau2-dbg
• libdrm2-dbg
• xserver-xorg-core-dbg