The UK Ministry of Defence (MoD) has begun releasing its voluminous files regarding unidentified flying objects, aerial phenomena, possible alien visitations etc. The documents will all become available to the public via the National Archives over the next three years.
UFOs of various kinds have been sighted and reported to the MoD and its predecessors for at least a hundred years. In general, the number and nature of sightings is much more affected by things such as movie releases or war scares than by any other apparent factor, all the way back to the "Phantom airships" widely reported in the UK before and during World War One - when panic about German zeppelins was at its height.
Many of the MoD's UFO files - including, probably, most of the good stuff - have already been revealed under Freedom of Information Act requests. In particular, the splendid conspiracy fodder surrounding the Rendlesham Forest incident of 1980 ("Britain's Roswell") has long been available, full of mysterious lights, strange marks left in the ground and traces of radiation. Even better, the cameras recording the British air-defence radar picture were switched off at the time, indicating an almost certain government conspiracy.
Anyway, the previously unseen bumf is all coming out from the National Archives here. The files will be free for a month after each one is released, after which there will be a fee for access, so enthusiasts should keep checking back and downloading the stuff as it comes out. (Be warned though, the MoD says upfront that it has never found any solid evidence of aliens, secret American hypersonic stealth spyplanes or anything else good.)
After three years, if you keep it up, you'll be the proud owner of a complete uk.gov UFO archive.
Or, depending on your viewpoint, <tinfoil>you'll be the owner of the biggest and most comprehensive cover-up ever compiled</tinfoil>. ®