Ending today, Crocs takes 25% off sitewide during its Presidents' Day Sale. (Discounts apply in cart.) Shipping adds $4.99, or get free shipping on orders of $24.99 or more. A couple of best bets, with prices after discount and $4.99 for shipping:
Eastbay offers the New Era Men's NFL Knit Beanie in nearly 100 styles for $9.99 with free shipping. That's a savings of up to $15. Most teams are included in this promotion, although the New England Patriots and Atlanta Falcons are notably absent.