Over the past four years, the price of gas has almost tripled and, even if hybrids and fuel cells and ethanol all accelerate their production and begin bearing fruit, worldwide demand will probably keep the cost of gas at somewhere near its current price. At least, that's the concept behind MyGallons.com and GasBankUSA, two companies that allow members to lock in today's gas prices for future fill ups.

Basically, it works like this: MyGallons and GasBank both charge customers a yearly membership fee. At MyGallons, it ranges between $29.95 and $39.95, while GasBank charges $19.95. Members can then purchase gas at the current rate. Their gallons are recorded on a debit card, and they can withdraw gas from their accounts at a later date. Of the two, GasBank is a better bet right now, as MyGallons has yet to set up a national network for its card.

This system has a few dangers: if gas prices drop, as they're likely to do when the summer gas spike is over, then customers will be stuck with a card full of $4.20 per gallon gas. On the other hand, filling up a prepaid card in February might be a pretty good idea, as it could help consumers lock in their summer vacation gas at cheaper winter prices. Similarly, loading up before the Thanksgiving/Christmas rush might be wise.

Of course, in the long run, gas prices are likely to continue rising, so saving money by prepaying may just be a matter of taking a very long view. It's not too hard to imagine some kid finding Grandpa's old gas card twenty years in the future and using it to buy AT&T. In the meantime, it might be a good way to save some money on your weekly fill-ups!

Bruce Watson is a freelance writer, blogger, and all-around cheapskate. He's starting to seriously think about that gas card/AT&T takeover idea...