If you need to do some serious maths/statistics stuff or just number crunching, there’s plenty of tools out there.
Being a happy Smalltalker/Pharoer/VisualWorker/VisualAger/Dolphiner/Squeaker, my favorite library is PolyMath (previously known as SciSmalltalk). Otherwise, I’m a big fan of R (mostly because of the huge amount of packages available). Hey! That’s a long way from my nightmare days of SAS and SPSS!
Most complaints I hear about R is its inability to deal with large amounts of data and somewhat annoying syntax/style (I don’t get it!!!).
But there’s always Julia. Give it a try!