Fisheye lens for my DSLR camera?

I want to buy a fisheye lens for my nikon d5000 SLR camera. I'm a serious photographer, but am not sure how much I would use this special lens, so I want to get one that is not too expensive. A good off-brand would be fine. Any suggestions? Please, 100 dollars or less would be great! I don't really know anything about fisheye lenses.

Added (1). I'd like some specific lens suggestions, please. What kind did you get?

I got a pretty good fisheye on E-BAY for less than $40.

I guess the first thing is that you need to decide how much you are going to use such a lens. It is important that know that you will be using it enough to justify the $350 to $1, 200 for a true fisheye lens, a lens that can see a full 180 degrees.

For under $100 (closer to $40), you will only be able to find toys that distort the image like a fisheye does, but can't cover the full 180 degrees that describes a fisheye.

Here is a sample of what a fisheye lens sees

As you will notice, there are drawbacks to using a fisheye lens.

* people standing next to you will be part of the photo
* any shadows being cast are difficult to avoid
* your feet may show up on the shot as well.
* any thing hanging off the camera (like a neck strap) could get into the shot.

Why are you wanting a fisheye?

they are gimmicky and expensive for the good ones…

save your money and get a decent lens that you might use for more than a couple of weeks… Then use image editing…