polar surface area calculator for proteins

[Jenn]

Hello,

I'm looking for a free program that can calculate the total surface
area, strongly polar surface area, and nonpolar surface area of a
protein from a PDB file.   It would also be nice if the program
allowed me to choose certain residues to base the calculations on.  
Does such a program exist for Windows based boxes, Macs (OS X) or
Linux/UNIX?

Thanks.