Today only, you can get 25% off at Old Navy with the promo code ONSPRING. Old Navy has a ton of inexpensive dresses right now too, so you can get some really great deals right now.
If you give this a little time, you can still get some discounts, but it's one of those "vanishing" promotions. Today you get 25% off, 4/15 and 4/16 you can get 20%, and then 4/17 you get 15% off. Obviously, you'll want to use this today!