I didn't want to spend more money buying a special pump JUST to blow up the mattress, so I did it orally (yah, that sounds slightly obscene)...this was when I discovered that you can make yourself faint by hyperventilating.
There's gotta be a better way. Here it is.
Step 1: Materials
*Plastic valve used for inflating beach balls, swim floats, etc. - you can find these in sports stores or even sports departments of ordinary department stores. One end screws into the Schrader valve adapter of bicycle pumps. (Schrader is the big one, Presta is the skinny one for special tires.)
ShapeLock or other low-melting thermoplastic - these plastics melt at less than the boiling point of water, but become quite hard at room temperature
*Oil - pretty much any kind will do; cooking oil, Vaseline, machine oil, baby oil, whatever
*Vessel for boiling water in
*Fork, tongs, chopsticks, or other tool for handling hot substances
*Small knife, compasses, or other pointy thing
*Air mattress (the one you want to inflate, obviously, but I think the valves are standard sizes)
Step 2: Simple, Straightforward:
Put about 2-3 tablespoonsful of ShapeLock pellets in a bowl and EITHER pour boiling water into it and let it sit, OR put tap water in the bowl and microwave it till the pellets melt. The plastic turns from white to transparent as it melts.
Try to push the pellets together into a single lump with a fork or chopsticks, avoiding air and water bubbles as much as possible. It's incredibly sticky, by the way, so don't use your fine porcelain to melt it in.
Pick it up and wrap it around the valve, using fingers to help as soon as it's cool to touch. Don't get it into the screw threads or the hole at the tip. Try to make the lump of plastic slightly wider than the inner diameter of the air mattress valve.
Grease the inside of the air mattress valve so that the plastic won't stick. When it has cooled down to about the hardness of plasticine, stuff it into the air mattress valve and hold it there until it's hardened.