One of my favorite Guatemalan desserts involves plantains! For a special meal, we made these little balls of mashed plantains, fried them, and then rolled them in cinnamon and sugar. I think we put something in the middle too...but now I'm not so sure.
The recipe below is pretty similar, only it adds refried black beans into the mix, which sounds kind of odd, but who knows?
http://www.virtualcities.com/ons/nm/f/nmfb1011.htmYou can also cut the plantains into thin slices, fry them, and top with salt and chile powder. Delcious snack!
Finally, I think you can just boil them, mash them, and add your favorite flavorings (maybe some butter, queso fresco, etc.) for a nice side dish. You just want to make sure that you get green plantains and not ripe plantains for that idea.