If you don't mind the laptop degrading due to heat, you can get
cgminer working on MacOS X. I'd recommend enabling CPU mining (if it's just going to be sitting in a corner) by changing the configure line in the instructions to:
./configure --enable-scrypt --enable-cpumining
You might also want to have it start when your system boots.
You can then try it out for a bit and see whether it's worth it to let it continue.