GRTensor is a very handy Maple package for doing calculations in General Relativity. Given a specific metric, it’s great at calculating the components of tensors. You can define your own tensors or use the predefined ones. You can even define your own metrics.

Unfortunately, getting it working on Mac OS X is a bit of a pain. This is due to a bug in GRTensor that has gone unfixed for quite a while. Fortunately, there is a straightforwarde solution.