SpeedFan is pretty good. That's what I use. However, I don't know if it'd be right for you, I mean, just look at the name . But it monitors any system temperatures except for your graphics card, I think. Other people use Everest and some other thing that I can't think of the name right now...
Use RivaTuner for your video card, though. It is really good.
Use RivaTuner for your video card, though. It is really good.