Here's a couple of excellent sources for royalty-free music:
incompetech.com - Kevin MaCleod is basically a genius and a prolific one at that. He has a huge range of music here and all he wants is a credit. His "silent movie" music is brilliant. His other main strength is dark piano music but there's plenty beyond that.
musopen.com - loads of classical music here. It's "public domain" music because the copyright has expired but I'm not entirely sure it can be used in video projects for profit (from the performer's point of view).