Mossberg is a pretty well known brand for shotguns. My local stores sell the Mossberg500 with 8-shot capacity for $319 (used to be $299, no thanks to inflation). Thats a pretty good price IMO.
Budsgunshop.com is a good place to start online.
If you had the extra money lying around, I'd recommend the Benelli M4 semiauto shotgun. But it retails for $1600 !!!