Oregon Caves National Monument Boundary Adjustment Act of 2008 - Adjusts the boundary of the Oregon Caves National Monument (Monument). Directs the Secretary of Agriculture to: (1) transfer certain acreage in the Monument to the Secretary of the Interior; and (2) adjust the boundary of the Rogue River-Siskiyou National Forest to exclude certain lands in the Monument transferred by the Secretary.
Amends the Wild and Scenic Rivers Act to designate certain additional segments of the Monument as components of the national wild and scenic rivers system.
Requires the Secretary of the Interior to: (1) administer the Monument in accordance with this Act and other legal authorities; and (2) carry out forest restoration activities within the boundaries of the Monument.
Directs the Secretary of Agriculture or the Interior to accept any grazing lease or permit that is donated by a livestock operator that holds a valid existing grazing lease or permit for a grazing allotment.