A friend of mine owns a 5D mk2 which he was using in some moderate rain recently with a weather sealed 70-200mm lens. Everything seemed fine afterwards, but the wheel on the back of the camera did go a bit funny, as did the 'Set' button. As far as I know, all is well now, after a trip to the airing cupboard!
The 5D seems to be the de-facto wedding camera, along with possibly a 1D or 1Ds. The 7D would be pretty nifty in place of a 1D if you take price into consideration, but of course bear in mind the crop factor. It's handy for the longer lenses, but does sorta limit your abilities with the wide angles.
Something like the following would be ace, which covers most focal lengths (bearing in mind crop factors)
5D mk2 + 16-35L + 24-70L or 24-105L
7D + 70-200 f2.8