I wanna buy a professional digital camera.which model do you offer?

it'll be between 5-10 megapixels.i'll take not only nature but also moving photos...

Get a DSLR. I suggest Nikon or Canon. Start with the enthusiast models (Nikon D50 or D70 or the Canon Digital Rebels are both great ones to start out with). If you wanna go for the gusto, try the Hasselblad digital, it's around $25,000 for around 22 Megapixels, but it's a helluva camera.

panasonic or fuji

buy a canon sd550,
it's a great camera. you'll absolutly love it....

There is one very good prosumer camera Nikon D50, it's less than $600 with the lens. good deal! just bought couple of months ago and having fun!

If you are ready to spend more money, you can buy Canon D20..great Camera!

I would suggest only Canon. Checkout for cameras at wolfcamera.com