$13.95+: Low daily car rental rates in major cities Through 2008
Hotwire.com

$9/day+: Save at over 13,500 car rental locations Through 2008
CarRentals.com

15% off: Alamo rental cars at participating locations Through Dec 31
Alamo

Under $10+: Cheap car rentals in major cities Through Aug 31
CarRentals.com

Up to $3 off: Trips to & from airport w/SuperShuttle Through Dec 31
Super Shuttle

Up to 10% off: Any vehicle at Dollar Rent A Car Through Jan 31, 2010
Dollar Rent A Car

$23/day+: Daily car rentals in sun destinations Through 2008
E-Z Rent-a-Car

$30 off: Weekly car rentals; no blackout dates Through Dec 2008
Hertz

$13.95+: Rental cars in major cities like SF & LA Through 2008
Hotwire

Up to $50 off: Monthly car rentals in top cities w/Hertz Through Dec 15
Orbitz

10% off: Any vehicle at Thrifty Car Rental locations Through Jan 31, 2010
Thrifty