I just pre-spent a little of my XMas money and bought a large capacity float tube off E-Bay from a kindly gent who fishes in Washington state. He related to me a trick for inflating it. Some of you may already know about this, but to me it's the most innovative thing I've heard all year.
Take an old scuba tank -- one that's too old for continued underwater service (you can pick these up for next to nothing at a scuba shop). Rig the float tube's filler nozzle to the tank outlet (a little sketchy on the details, but it sounds like a doable winter project). Open the valve with the nozzle in the float tube and whoosh!! You're done in under 20 seconds. Just be careful not to over-inflate!!
I've seen some battery operated pumps that can take as long as ten minutes to do the same job.
One detail I'm still a little unsure of is filling the tank: does anyone know if scuba tanks can be filled using a "regular" air compressor such as might be found at a gas station?