Aeropostale takes up to 70% off most items sitewide. Plus, take an extra 20% off via coupon code "HELLOAERO". Shipping adds a flat $5, a $2 discount from its normal cost. Deal ends August 28. A couple of best bets after coupon:
Aeropostale via eBay offers the Aeropostale Men's A87 Solid Pique Polo Shirt in Black or Bleach, for $13.99 with free shipping. That's $5 less than what Aeropostale direct charges. They're available in sizes XS to 3XL, although not in all size/color combinations.