Replying to Fish eye lens, Nikon D50

Hey i searched barred for fish eye lens didn't get much info and threads were kinda dated. So I am looking for a good fish eye lens that is not in the $1000 range, more the $300-600 range. That is if a fish eye lens that price is even worth getting? Also i am kinda new to photography and any good retail stores that may be good to know for future reference?
I know this probably should be in gear talk, but i figured it would get more attention here.

thanks, NS