I commute to my college every single day and I bring this thing with me. It's a Thinkpad T420 with an Nvidia Quadro NVS 4200M, which can crunch out 10 Mhash/s using the OpenCL miner. I can mine for two to three hours every weekday in the library between classes. This means that electricity is free.
I use BTC Guild for pooled mining.
I used to mine on GTX 560 Ti many months ago, until the falling value of BTC made the whole thing unfeasible.
Don't bother. The extra heat and stress on the laptop will greatly accelerate any failure, besides the fact that that is a fairly expensive video card anyway.