Sure, once your tank is ready for coral you can add zoas, mushrooms, star polyps, lots of cheaper corals. You can always check the classifieds on here as well, although if you are just buying one or two frags shipping will kill you. Best bet is to go to your lfs and see what you like, then before buying come on here and ask whether or not it would be good for your tank. Then the next day, if everything is on the up and up go and buy them.
You would only really need to do this when you are a beginner. In the meantime do your research and find out what you like and what you want in your tank.