Dude, If you have a boat already it is probably the best one to start with. If you don't, you can't go wrong with a jon boat. There are lots of them out there and if you're patient, they're pretty cheap.
I shoot off a pontoon myself and love it for the comfort, but I've seen almost every kind of small boat used. At the last tournament we went to a guy had a deck boat rigged up.
check out this link,
http://www.illinoisbowfishers.com/ClickGallery/gallery.asp?currentpage=1
There are pics of lots of different styles of bowfishing rigs.