Monitor calibration is critical for photographers. There is no point in trying to do extensive post production on an image if you have no idea what your monitor is actually displaying.
To this end I use the X-Rite i-1 Display 2. This is a version of their profiler that is no longer available.
When OS X Lion was released many people were surprised that their Profilers no longer worked. Unfortunately the profiling software was written for Macs with PowerPC processors. Until Lion, all Macs came with translation software that enabled them to run software written for the older Macs.
Luckily X Rite have released a native Intel version for Modern Macs running OS X Lion and even for older versions like mine. If you are a registered user you can login and download the new version.