Old Navy takes up to 50% off sitewide. Shipping adds a flat-rate $7, or get free shipping on orders of $50 or more. Discounted items include swimwear, activewear, khakis, jeans, and button-up shirts. A couple of best bets, with $7 for shipping:
Old Navy Men's Ripstop Utility Shorts from $12 (pictured, $13 off)
Old Navy Women's Striped Linen-Blend Romper for $26 ($11 off)