I want a fisheye lens, but I don't want to spend 500$ on a real fisheye unit. What to do?
I saw this cool post: http://photojojo.com/content/diy/make-your-own-fisheye-lens/
And decided that I could do one better: I would go to an eyeglasses shop and get the highest prescription lens-blank they had.

Items needed:
A digital camera (SLR or point-and-shoot)
If it's an SLR, you also need an 18-55 lens, stock with most cameras.
Very thick, uncut eyeglass-lens. ($15)

Step 1: Buying the Lens

Buy a blank, uncut lens from an optician.they come in either +sizes, which are convex and will do the opposite, and -size concave lenses, which make the magic happen. I am using a -8.00 hi-index lens. Don't buy the compressed plastic kind either, you want super-size coke bottles

Step 2: Holding the Lens, Over the Lens

Wash your hands! Keep the lens clean. Hold the lens in front of the camera.
If you're using an SLR lens, zoom it out to the widest possible setting (i.e. 18mm).
If you're using a point-and-shoot, make sure it's set to "macro" mode (flower icon) so it can focus.

The lens does different things, depending on which way the concavity is facing. For clean photos, with less distortion, hold the eyeglass lens directly against the camera lens. For a little more distortion, pull it a few cms away, as shown in the photo. This is the reason I didn't tape it down, I like the variety that can be had by adjusting the distance of the lenses.

Step 3: Take Photos!

Experiment! The lens can be flipped and used both ways. Holding the curved side towards the camera gives cleaner images. Flipping the curved side out will give much more "fisheye-osity" but it gets fuzzy around the edges. Same goese for distance between the lenses. Here are some samples: