This tool will allow in a simple manner to check what version of OpenGL you have supported on your displays + Shading language and wether or not Quartz Extreme is supported.
I redesigned this tool to also allow you to show display parameters like size and rotation (no rotation check on Tiger though).
It has optimized versions for Tiger, Leopard and Snow Leopard.

Time to test...

Download including sources:
http://rapidshare.com/files/37235287..._Leo_Tiger.zip