I moved to a Linux system from Windows a few months ago. Most of the programs I had been using were already native to Linux (Firefox, the GIMP, Pari, etc.) and most others I found a close enough program (Crimson Editor -> gedit, Visual Studio -> KDevelop, Primo -> Morain's ECPP).
Now I'm down to just odds and ends. Does anyone have a close-enough equivalent for CurveExpert? It's a fire-and-forget curve-fitting program, very nice.