Deal.Fisher via eBay offers the refurbished Netgear N900 802.11n Dual Band Wireless USB Adapter, model no. WNDA4100, for $22.50 with free shipping. That's $33 under the lowest total price we could find for a new one. It features up to 450Mbps data transfer rate.

A 90-day warranty applies, but it is unclear who backs it.