TigerDirect offers the D-Link 802.11n Wireless Pico-Size USB 2.0 Adapter
, model no. DWA-121, for $19.97. Coupon code "COP64024" cuts it to $4.97
. With $2.29
for shipping, that's the lowest total price we could find by $15. (It's also the least expensive 802.11n USB adapter we've seen of this size.) It supports speeds up to 54Mbps, WPA and WPA2 encryption, Wi-Fi Protected Setup, and more. Coupon expires after 400 uses.