If you're camping or have guests over, inflatable mattresses are handy. If you can't find a pump, you'll tire quickly inflating it yourself. A garbage bag inflates your mattress and saves your lungs.
Open up a big garbage bag (they call it a bin bag in the video) and catch a bunch of air in it. Seal the end of the bag to the mattress and lay on top of it. You'll need to do it a few times to inflate the mattress, but it sure beats trying to blow into it for an hour.
Check the video for the walk-through.
How to Inflate an Airbed Without a Pump [YouTube]