West Marine sells a bunch of these little boats. I've ridden on the SB-275 and it's a lot of fun. It either had a 1.5hp motor or a 2hp. Plenty fast unless you want to set speed records with something bigger. When you're shopping for a motor; pay attention to the weights of the motor. The little ones are lighter and cheaper and they start getting more heavy and expensive in a hurry.
Boat was reminiscent of a Jet Ski or Wave Runner when going fast or on choppy(wavy) lake water. Boat skims over the surface of the water instead of pushing through the water. Boat handled perfectly fine and normal at lower speeds(we were racing around going flat out).
Absolutely handy and indispensable to have on hand so that any body of water that you are at you can explore. Pumps up fast and the motor clamps on to the transom. West Marine also sells a motor that runs on Propane.
Many larger ships use these inflatables to run to shore with.
A few videos of the different models:
http://www.youtube.com/playlist?list=PLF21D50B61BF1E546
This page has a lot of good info. Pay attention to what type of floor it has as that will determine how small the boat will pack up:
The West Advisor: Inflatable Boats
They go on sale often and I think the prices are negotiable too in store.
This place also has a good selection of different brands:
http://www.defender.com/categoryBoat...570&id=1794282
I plan on getting one myself in the near future. Great to be able to get out on the water at any moments notice.