Buy a $2.99 Saver Sack using this White Castle coupon
and get one Saver Sack free. Expires Aug. 4, 2010. The Saver Sack includes two sandwiches (they're small), a "saver size" fries and a "saver size" fountain drink. It's unclear how small "saver size" is, but I'm guessing pretty teeny.
Caveats: one coupon per customer per visit. Valid at participating locations only.