Yep, just apt-get install nvidia-cuda-toolkit. It's currently v5.5.22 (a mid-2013 version). Debian started working on a packaging of v6.x in the "experimental" repository a few weeks ago, which will probably migrate to regular Debian and Ubuntu releases once it's tested a bit.
I actually tried this a few months ago. I had some issues trying to run the typical vector addition "Hello world!" examples on my system.
I'm not 100% sure but I also think that by installing the nvidia-cuda-toolkit package it leaves out the CUDA samples. These contain the deviceQuery and bandwidthTest scripts necessary to check that CUDA is functional.
Admittedly I have two consumer cards in SLI, so that may have affected the install. It could also have been incompatibility between the actual Nvidia display drivers and the various dependencies. It's a bit messy!