Newegg offers the refurbished TP-Link N600 802.11n Wireless Dual Band USB Adapter, model no. TL-WDN3200, for $12.99. Coupon code "EMCAVKV35" cuts that to $9.09. With 99 cents for shipping, that's $13 below the lowest total price we could find for a new unit. It supports speeds of up to 300Mbps on either 2.4GHz or 5Ghz channels. Deal ends July 20.
A 1-year warranty applies, although it's not clear who backs it.