I just saw
this interview (which British people probably won't be able to watch) with an author of a book about Area 51. Her research claims that aliens were never taken to the base, but that lots of other shit went down there. Much top-secret research in to nuclear weapons and unmanned drones and whatnot. So secretive that the people there decided that Bill Clinton wasn't important enough to know what was going on, when he was president.
Also, she claims that the Roswell incident was actually Stalin sending over a 'spacecraft' with fake aliens (possibly actual Russian children) in order to provoke panic in the USA, War Of The Worlds-style.