SOFTWARE

PROPEP Calculates: propellant density, chamber temperature, exhaust temperature, composition of chamber/exhaust gases, specific heat ratio, specific impulse (frozen and shifted), characteristic impulse and density impulse. There is also a calculation to calculate the optimum nozzle expansion. (source info)

BurnSim Complete burn simulation for Bates and D-grain motors.  Shareware.  Free 7 day trial and then $25 to register. (source info)
KnCulator v1.1.5 A Windows program for calculating Kn values.  Invaluable for chosing the correct nozzle throat size. (source info)                                                                                                           
KnCulator v1.1.8 This version will work with BurnSim.  The 1.1.5 version won't.  Otherwise, it's the same.  This is just the executable, you'll need to install v1.1.5 first and then replace the application with this one. (source info)