Also - just to point out (incase you didnt know already)
Certain lenses will only go on certain brands of camera, and on certain lens mounts on those cameras.
For example - A Canon EF 50mm F/1.8 lens will only work on Canon cameras that have a EF mount, which include all EOS Camera, Film and Digital SLR cameras.
Once you start to buy lenses, esepcially the more expensive ones, you are sort of commiting yourself to the brand of the camera body you have, e.g. Myself in the Canon brand, any other DSLR body I buy will be a Canon so that it fits my exisiting lenses (and ones I plan to buy soon!) even though this won't be for a while.
So it is kind of a commitment. Nikon make some fantastic kit, there is no doubt about that, and also some fantastic lenses (18-200VR

) so, its all about who you plan to stay with in the future in my eyes.
Whichever brand you decide to go for, go to their sections in the forum to get advice on lenses and other things!
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Canon EOS 5DmkII + BG-E6 + Canon EOS 40D + BG-E2N + Canon EOS 33
Canon 17-40
F/4L USM + Canon 24-70
F/2.8L USM + Canon 28mm F/1.8 USM + Canon 70-200
F/2.8L USM IS + Canon 85mm F/1.8 USM
Canon Speedlite 580EX II + Canon Speedlite 540EZ + 2 x Nikon SB-80DX
Cactus V2s Wireless Trigger -
5 x Cactus V2s Wireless Reciever
MY FLICKR!