Mac OSX Temp and Fan monitor

SMCFanControl is popular and easy to use. I would recommend it. You can view your temp in F/C as well as the fan speed in the toolbar at the top, and you can set the minimum fan speed.

 

iStat Menus 3!

More BANG for your BUCK.

 

I prefer iStat Pro. It gives you information about far more than temps and fans.

 

I have iStat Pro for all my monitoring, but since it doesn't control fan speed I use SMC fan control to handle fan speed. I took the time to create speeds for every 500 RPM from the standard 2500 all the way up to 6500 max. That way I can adjust accordingly for the temps and still get a balance of battery life.