Recommendations: Which wide-angle lens should I purchase? (Nikon)?

I really need help deciding on what lens to buy. A sigma 10-20mm lens or a Nikon fish eye. What I'm obviously aiming for here is a wide angle lens. Pretty much, I'm looking to shoot more landscapes, something I'm passionate about; however, I'm having trouble on what to purchase since most "good" lens' are $1000+.

Here's my other problem, I'm looking for a lens that isn't that expensive as well. Since I'm not a "professional" at the moment and is still learning, I figured I shouldn't spend that much money on a lens and rather wait until a later time.

I would very much appreciate it if anyone can give me a list or your recommendations on a acceptable lens to purchase. Feel free to suggest other things as well.

I'd go for the Sigma 10-20mm an excellent lens in two versions - f3.5 or f4-f5.6 (the variable aperture lens is cheaper).

The Nikon fisheye will be more expensive and more limiting in what you can do with it.

I have the Sigma 10-20mm f4-f5.6 on a Nikon D300 & am very pleased with it.

Example images here from the Flickr Sigma 10-20mm group (all different camera bodies);

The Sigma 10-20mm f4-5.6 EX DC HSM has gotten good reviews. One nice feature of the lens is it has a Distance Information Function. This will prove useful when you're shooting your landscapes and want to maximize your Depth of Field (DOF). At B&H its shown for $479.00 so its not overly expensive. It should be sufficient for your needs.
http://www.bhphotovideo.com/...ovideo.com

However, if you don't have a tripod then you definitely need to add one to your shopping list. In my opinion a tripod is mandatory for good landscape photography.

Maximizing your DOF is something you'll also want to do. At 10mm and f16 if you focus on an object 5'-0'' from your camera your DOF will be from about 10" (0.86') to infinity. Anything from approximately 4'-2'' in front of your subject to as far as you can see - infinity - will be in focus. This site will allow you to choose your camera and compute the DOF for any combination of the three factors that affect your DOF: 1) Lens focal length; 2) Aperture used; 3) Subject distance.

http://www.dofmaster.com/dofjs.html

I shoot all of my landscapes with my camera in Aperture Priority.

A 'fish-eye' has a single application - that odd bulging shape, but a wide zoom such as 10 to 20mm has more versatility. You can fake the 'fish-eye' style in most imaging softwares in your computer.

No good wide angle or fish-eye is cheap, design constraints preclude a good cheap wide angle; cheapish good medium-range tele zooms are possible - simple laws of optics.

Go for the Sigma. You don't want to get stuck with only fish eye pictures.