Mining runs your computer hard. You can take steps to run it easier, but you're not going to get much speed out of nvidia I'm afraid. And if it's integrated graphics - nothing at all. What Mac do you have? A Mac Pro is fine. Anything else, a little risky.
That said, I recommend MacMiner
https://bitcointalk.org/index.php?topic=197110.0You can probably guess why
Just make sure you know what you're doing if you're going to mine. Check out the options you can use like -f 0-60 for poclbm or -I -10 to ~14 for cgminer/bfgminer, check your temperatures, maybe rev up the fans with smcfancontrol