If you go to Old Navy's Website you'll find random coupons for $$$ off your total bill by clicking through the site's links. According to Money Savin' Momma:
The Old Navy Weekly coupons will reload on Sunday, 5/31/09. Check out the Old Navy Weekly website to get some of these coupons. This includes coupons like $75 off a purchase of $100 or more, along with other coupons! You simply click around the site and find coupons.
Keep a close eye on the site to catch the reloads, as the coupons may be reloaded at different times during the week, and they may be reloaded several times throughout the week! (And no, we don't know the exact reload times - Old Navy wants to surprise us, but they have said it will be Sunday, 5/31/09!)