Prices have been helped by the US tapping the strategic oil reserves three weeks ago, under the auspices of replacing production capacity lost in the Florida hurricaines, and by federal subsidies to oil producers in the 2003 energy bill.
There are a lot of things the US gov't can do to keep gas prices down. Ultimately it costs just as much, but Americans are a lot happier, on average, if their government adds $10 billion to the debt, and drops gas prices at the pump by a penny, than if they had to pay the higher gas price out of pocket. The government institutes these sorts of subsidies fairly regularly, so it's never any one obvious factor, it's usually just a penny or two here and there.
