There isn't much support for Nvidia cards, especially with the GTX 680. But a member did compile a small miner to test out:
I have tried to recompile the Ufa-miner and the rpcminer-cuda, but for various reasons it didn't work.
Now I have written a very simple miner using the latest CUDA toolkit, just to see what the speed is like.
Since I have written the kernel from scratch, and the program is not doing longpolling, there's some room for improvement.
If somebody with a GTX680 would like to try it you can download it there:http://www.sonstiges.org/bitcoin/ICU-Miner.zip
ICU-Miner.exe URL username password devicenumber gridsize blocksize
(devicenumber, gridsize and blocksize are optional)
ICU-Miner.exe http://mining.eligius.st:8337/ 1BtVLjUkAzF9wZGHfKzzsPivgNAn4DTp1Q joshua
Here's the ugly source code:http://www.sonstiges.org/bitcoin/ICU-Miner-source.zip
Unfortunately it didn't do as well as we had hoped. The most I was able to get out of it was ~94 Mh/s.