Do you know any good software for manipulating tensors: varying Lagrangians, checking gauge and supersymmetry transformations, etc. ? One that could deal with anti-commuting variables would be good too. One that also supplied group constants for SU(n) etc. would also be useful. I was also looking for some simple software that knew that AxB +BxA = 0 for cross products of abstract 3-vectors but couldn't find any.