GDL .. a free IDL
Many among us, in the Mac scientific community, use IDL, a sophisticated data visualisation and analysis platform by ITT Visual Information Solutions (formerly, Research Systems Inc.). It is particularly popular in astronomy/astrophysics and also biophysics/medicine. IDL is commercial software and is amongst the most expensively licensed packages, I have ever used.
There is a free alternative, which is not quite as well known. This is Gnu Data Language or GDL. It is fully compatible with IDL 6.0 and it appears to work very well. It is fully supported on Mac OS X (Intel/PPC). The main project developer, Marc Schellens, is an excellent person to interact with, on matters of bugs, features, fixes, etc.
If you're an IDL user, you may want to consider GDL at some point. It works well and is really easy on your research grant's budget!