I've been reading up on Paul McCartney lately and it turns out that he's been dead since 1966. Little did I know, he's been played by a guy named Billy Shepherd, or Billy Campbell or something like that shutupandbelievemefool.
I think this is the most convincing "believer" site I have read.
The autor of the site says that McCartney's death was an accident. The CIA was actually trying to off his manager Brian Epstein. While that whole plot seems shaky, it does fill in some holes in other conspiracies. Such as, why did the Beatles keep his death under wraps? This site explains that they did it to keep the CIA off their backs.
This one's disturbing.
The very first picture of "Paul" (Billy Shepherd?) naked. (He's covered enough to be safe, but just barely.) Those gifs of the morphing faces are really creepy too.
I think the credibility of the site is undermined for several reasons. First of all, it refers the alleged impostor as "Billy Shepherd." Just about every other source calls him "Billy Campbell." Secondly, it lists Paul's date of death as September 11, 1966. This is probably a misunderstanding of the actual date given by most theories of 11-9 (November 9). The site has a .it ending, so the writer probably assumes the European custom of date before month. The writer might also be looking for some 9-11 connections.
From the BBC's h2g2 network.
This source seems pretty skeptical. It has a lot of things that seem to add up, though. Some of the stuff is kind of creepy.
This one's in-depth.
It believes that the "Paul is dead" theory is fake, but it goes into more details and clues than I've seen anywhere else.