Bil Simser has an excellent post about how to work with Subversion and how to employ the branching and tagging features. If this does not convince you to switch over from SourceSafe, I don't know what else would ;-)

While you're at it, take a look at VisualSVN! It's the best integration into Visual Studio of Subversion I've met. It comes at a very modest price (currently $49) but it is worth every penny. Second, they have VisualSVN Server, a free GUI frontend to Subversion, complete with MMC and integrated Apache webserver.