Most FE preprocessors and CAD programs have quite good section properties modules. PATRAN, Femap and CATIA all do the job.
There are a million billion (almost) simple programs and spreadsheets out there too. Quite a common approach that appeals to people is to define the section by a series of points making up a complicated polygon, and then to find the properties by evaluating a series of trapeziums, one between each side of the polygon and each of the X and Y axes.
One older program that works well is the BEAMSTRESS module of the old SMUG suite (Structural Members User Group). This handles the slightly trickier aspect of torsional properties of an arbitrary section. Boeing's SA can also do this, though it has to make a mesh and do an FE analysis (which it is quite happy to do). BEAMSTRESS requires you to make the mesh, but it works (also by FE). Unfortunately I can no information of SMUG or its BEAMSTRESS online, though my company still has it available on the computer system.
I know of no software that does plastic torsion, and although I suspect that plastic bending is occasionally covered I actually don't know of any that does that, either. In these instances a full plastic FE analysis is probably the only way. Plastic torsion is rarely covered in classic texts. "Inelastic Behavior of Load-Carrying Members" by J.O. Smith has something on a limited set of sections.