Newegg offers the refurbished Asus 802.11n Wireless USB Adapter, model no. USB-N13, for $14.99. This $10 mail-in rebate cuts the price to $4.99. With free shipping, that's $15 under the lowest total price we could find for a new unit. It features data transfer rates of up to 300MB/s. Rebate expires August 19.

A 90-day warranty applies, although it's unclear who backs it.