I've used this free program to make lots of diagrams: http://pencil.evolus.vn/Downloads.html http://pencil.evolus.vn/Downloads.html I don't know if it's the be

I've used this free program to make lots of diagrams: http://pencil.evolus.vn/Downloads.html http://pencil.evolus.vn/Downloads.html I don't know if it's the best thing out there, but it's pretty low risk to try it out. I haven't needed to look for anything better, and it does have some neat features.