Generally the guts of a program are self-contained within the application bundle, so you can delete that. They're the .app files. There are some configuration files that apps tend to store elsewhere, but generally they don't amount to much. Apple really needs to implement some sort of uninstall process so you can remove those files incase they DO amount to a bit, sometimes more than the app itself. You can uninstall things from the Mac App Store however by going into Launchpad, holding the app down, and clicking the little "x". This only works on apps downloaded from the store.