It's back again - Groupon has a $20 Old Navy gift certificate for only $20! Grab one before they sell out!
Just be sure to use it before December 24, after which it will only be worth the $10 you paid for it. That's the nice thing about Groupon . . . even if you forget to use it before the expiration date, you still get what you paid for it. Essentially, you just lose the "bonus" part of it.