and welcome to the forum.
For starters, Nikon - excellent choice!
For beginners DSLRs, as ALwin said you are limited to the D3100 and the D5100. Both, in my opinion, leaders in their price range.
However, don't rule out second hand cameras, as there are some bargains to be had. A list of older, but still extremely capable beginner Nikons include: D40, D40x, D60, D3000, D5000, D90 among others. All of these im sure would be more than enough camera for a couple of years, if not longer.
Lenses are something to consider too, but try not to get yourself too bogged down on all the different types just yet as it is a mine field out there. If you buy new the camera will invariably come with the kit lens, 18-55mm. This is a good all purpose lense, and is suited to wide angle shots and some general shots. These lenses are pretty good quality, and will be ideal for the majority of your shooting needs when starting out. However, lens choice really does depend what type of photos you want to be taking.
A good idea would be to get yourself down to your local Jessops and ask to play with some cameras. They won't pressure you in to buying if you dont want to, and the people that work there are usually very knowledgeable. They will also let you try a selection of lenses on a camera so you can see what you like.
Giving you all this information is all well and good, but ultimately with a hobby like this it all comes down to your budget, because photography is not cheap!