Ah! Thank god you have Nikon! Don't want you trying to go on Ebay and outbidding me - been looking for a while for a 10-20 under £250 thats in good condition.
Wouldn't buy the Fisheye 15mm for cropped frame for reasons mentioned above. I suppose there is some type of physical filter you can put on to give it a fisheye effect, that or you just use photoshop to do it until you buy a filter.
Canon EOS 5DmkII + BG-E6 + Canon EOS 40D + BG-E2N + Canon EOS 33
Canon 17-40 F/4L
USM + Canon 24-70 F/2.8L
USM + Canon 28mm F/1.8 USM + Canon 70-200 F/2.8L
USM IS + Canon 85mm F/1.8 USM
Canon Speedlite 580EX II + Canon Speedlite 540EZ + 2 x Nikon SB-80DX
Cactus V2s Wireless Trigger - 5 x
Cactus V2s Wireless Reciever