The Government has been working on Blackbook programs(Like Lockheed's Skunkworks program based out of Groom Lake or Area 51 for you amatuers

for years, it's nothing new. I think a lot of UFO sightings that people see are Military experimental Aircraft. I lived in Pahrump NV, about 40 miles from Area 51 when the Predator was being tested and that looked like nothing you've ever seen before if you see one fly above you. Also the Have Blue Stealth fighter and the Northrop Tacit Blue that they developed there looks like a UFO or something out of a Star Wars movie. Heres a link to a picture of the Tacit Blue.........
http://en.wikipedia.org/wiki/Northrop_Tacit_Blue and a link to the Have Blue
http://en.wikipedia.org/wiki/Have_Blue If you goto that page and the Area 51 page
http://en.wikipedia.org/wiki/Area_51#U-2_program it talkes alot about those two planes being mistaken for UFO's a lot.
Area 51 does exist and the Government has come public that it exists. I can provide a link to the page that shows you pictures and information on Janet Airlines (The flights that carry the workers daily from McCarren Airport in Las Vegas to Area 51, TTR, Edwards Airforce Base and the Stead Airport.)
If you look on Government papers it shows that Boeing, Lockheed-Martin, Northrop Grumman and McDonnell-Douglas(Which is interesting as I didn't think they were still around) all have hangars there. Everyone knows that all three companies develope top secret Aircraft for our Government. Also EG&G is the company that hires the civilian Security Force(Camo Dudes) and Scientists.
Aircraft that have been developed and tested at Groom include the Northrop Tacit Blue stealth demonstrator, various classified UAVs(like the Predator), and a stealthy cruise missile (most likely the AGM-129 Advanced Cruise Missile). Other rumored Groom test programs include a small stealthy VTOL troop-transport aircraft, the rumored Aurora hypersonic spy plane, a "Stealth Blimp", a secret USAF spaceplane codenamed Blackstar[11], and replacements for the SR-71 and F-117A. Also we have several Soviet Mig Fighters and Aircraft that we have obtained over the years and it is believed to be kept and tested there as well.
Also from what I read all the work are done in the Hangars, all the building have no windows and when a project is rolled out to be tested if your not involved with that project you have to be indoors wher eyou can not see whats going on, pretty creepy.
Is it possible that there is more to it then just Aircraft Research and Development of course. There probably is underground facilities etc. but that doesn't necessarly mean they have an Alien or are testing UFO's there, but it possibly could and I think that is part of the fascination with it. There are some really good pictures on the net of Area 51 taken by a Russian Spy Satellite and I would be happy to look up the links if you want. It shows that buildings are being added rapidly including a new Hangar that is bigger then any other Hangar in the country.
I also think that if there is an Alien conspiracy that Area 51 could be a cover for another Military Base to take the attention off of the place that is doing the research. One of the bases that is big with the UFO therorists is Wright Patterson Airforce Base in Ohio. A lot of them believe that it at one time housed the remains found in Rosewell.
If you want to go more indepth on this subject feel free to ask questions, I have read a lot about it being that I lived about 40 minutes away from there and now I still live only about 4-5 hours from there and pass by it every time I go to Las Vegas. It's beautiful at night the whole mountain is lit up like a Christmas Tree and you can see the Janet Flights come and go if you park off by the side of the road or stop at one of the places in the town right by there. It's also interesting that the only fights that are allowed to land there that don't take off from there are Janet flights. Even Military Aircraft are not allowed to land there or fly near it, even if you are having flight problems and have to land, you better make it to Nellis or McCarran. I read that they have a buffer zone and that when the pilots hit that they are warned because a lot of them don't know exactly where the zone is and if they keep proceeding after the warning that they can be Arrested or shot down. That is interesting as Military Pilots have to have a security clearance, so there is something there the Government doesn't want it's own people to know about.