Gas Price Spike Act of 2008 - Amends the Internal Revenue Code to impose a windfall profit tax on crude oil, natural gas, or products of crude oil or natural gas. Defines "windfall profit" as so much of the profit on a sale of crude oil, natural gas, or related products as exceeds a reasonable profit. Establishes the Reasonable Profits Board to determine levels of reasonable profit from the sale of such products.
Allows a tax credit for the purchase of certain fuel-efficient, American-made passenger vehicles.
Authorizes the Secretary of Transportation to make grants to operators of mass transit systems, including bus and commuter rail systems, to reduce passenger fares on such systems.