KenS sent me the link to these's folks website, and if I ever win the lottery (you gotta buy a ticket??) one of these is going to be a high on my list purchases.
The CraigCat, from CraigCat Catamaran Corp., runs up to 35 horsepower, and they are really stable, according to their website and the videos. In one video a 210 pound guy is bouncing up and down standing on one of the pontoons, and the cat is barely rocking. It looks like you could even use it as a mini bass boat!
For more info and to have a look at their action videos, check out their website.
It looks like a lot of fun!!