Gas Tax Relief and Earmark Moratorium Act of 2008 - Amends the Internal Revenue Code to suspend excise taxes on gasoline, diesel fuel, and kerosene between May 26, 2008, and September 1, 2008. Reimburses the Highway Trust Fund for any reduction in revenues resulting from such suspension.
Requires the Secretary of the Treasury to transfer amounts from the general fund of the Treasury to the Highway Trust Fund if the Secretary determines that the amount in such Fund is insufficient to meet anticipated payments for FY2009.
Establishes a Joint Select Committee on Earmark Reform to study and report on the practices of Congress and the executive branch regarding earmarks in appropriations, tax, and tariff measures.
Declares it not in order in the 110th Congress to consider legislation containing a congressional earmark, limited tax benefit, or limited tariff benefit.
Requires a reduction in the allocation of new budget authority and outlays for FY2009.