What do they attach to the video camera lens to achieve that fishbowl effect? ...such as in skateboard videos.

It is not where they attach it that makes it that way it is the lens itself.

a fish eye lense

not all camera are compatible with them though

one you are finish taping then you take the cd in a computer and do the effect on a special program

Thats a very good question....Cause them skateboard kids belong in fishbowls....

The high end vid cameras have replaceable lenses.
and a fish eye is a separate lens they run from like 17mm to 28mm Frankly there a bit pricey and while any good photog will have one in his bag it's almost not worth the price for how little they get used...

They use a wide angle lens (also known as the Fisheye Lens).

It's called a fisheye lens, funnily enough. This is a lens with a very wide angle of view.