The Obamas, the Sarkozys etc weren't invited because it's not a state occasion. They would have been invited if they were close friends, though. Also Blair and Brown weren't invited, but Thatcher and Major were; Tory conspiracy, perhaps?! ;D This is all on bbc.co.uk; you can get your Royal Wedding fix there!
I must admit I did like watching it, but it fucking dragged on. They looked bored to death. They also looked very tired; I bet they collapse into bed and put the shagging off until tomorrow!