Go here to print a coupon for a free shake with any entree purchase at Johnny Rockets. Coupon is good through May 31, 2009.
Also, you can sign up for the Johnny Rockets email club here and you'll receive a coupon for a free hamburger with a purchase of any hamburger or sandwich, starter, and drink.
Thanks, Stretching a Buck!
If your store is not participating, you can still get a pretty good deal at Carino's: when you sign up for their email club here, they'll send you a coupon for half off any entree.