What would be a good DSLR camera for nature photography?

You really want a crop sensor for wildlife. The crop brings the animal in closer, effectively increasing focal length.

I shoot Nikon, so my recommendations would be the D90 or D300s. It depends on budget, the D90 is around 750.00, and the D300s around 1500.00. They both have same sensor, the D300s has a higher frame rate and more metal in the body.

The lenses are the part where you need to spend the extra money. You need a 300mm lens at a minimum for wildlife, and an 11 or 12mm (cropped frame) at the wide end for scenic shots. Tokina lenses are really good glass, and a lot cheaper. Look for the 12-24 or the 11-16 for wide angle. For telephoto the 100-300 F4 is really good. They also make a really good 28-80mm 2.8 to look at.

The best approach would be to buy a D90, and have extra money for good glass.

Both of these shots were with the D300, the D90 has a slightly better sensor.

Here's a shot with the 100-300:

http://cgipix.com/Portfolio_Wildlife_Pronghorn_Ant...

Here's one with the Tokina 28-80mm 2.8:

http://cgipix.com/Portfolio_Utah_Vacation_Travel_A...

Any DSLR will do, full frame or otherwise. To be honest it's the lenses and the skill (and patience) of the photographer that are crucial for nature photography.

The Canon rebel range of cameras are very good for learning photography.

Any DSLR will do, but its the lenses that are more important.

Buy wisely.

Depending on what style of nature photography you want to do, a good quality 100-400 lens is what you need, plus a quality x2 converter.

depends what you mean by NATURE, that covers a multitude of sins...

flowers/insects

pets/domesticated animals

wildlife

use something like the Fuji HS10 - quite reasonably priced and goes upto 710mm...

failing that, any of the bigger DSLRS - Nikon D90/D3s/Canon 5D/Sony A850/A900 with something like the Sigma 150-500mm lens...

mine's Canon 450D, it works great.