I don't think I know of any self-respecting independent filmmaker that hasn't done a little dumpster diving in her/his life. (The best find: My friend Rob once reclaimed about a hundred unspoiled 16mm film prints of educational and documentary films, which a university library was throwing out. Mind-boggling.) If you're too proud, watch this
And regardless of whether you use Garbagescout.com when you dumpster dive, don't forget to whistle while you work