JPU — Just Plain Useful — tools for the Mac have been updated recently. Haven’t tried them, but might be worth a look: first, Aquaticprime is a free, open-source secure registration method for shareware applications; second, Sparkle, which is “a module that developers can stick in their Cocoa applications to get instant self-update functionality”.
Factory Joe 
Right on Chris. We all love to see these sorts of contributions to the Mac dev community.