GSAS and EXPGUI is another free and open source software package for Rietveld refinement that is well documented. I've always been able to google myself to an answer when I get stuck because of that. It may be a little clunky but it is in the process of being re-written in python for ease of use (GSAS II). I believe that GSAS II can handle most types of data sets right now except for TOF neutron diffraction. I'm not sure what kind of data you have so it may or may not be useful. There is a lot of good information on how to use it here:
oh I'm not a doctor yet, still a student. I defend in ~ 3 weeks but thanks just the same. The diffraction group at the APS that I linked to has some really great resources but GSAS can be tricky when you are first starting, I can try to help if you have any specific questions.