Amazon offers the refurbished D-Link DIR-655 Xtreme N 802.11n Wireless 4-Port Gigabit Router for $47.99. With free shipping, that's $5 under the lowest total price we could find for a refurbished unit, although we saw a refurb for $3 less last winter. (It's also the best price we could find for a new model now by $22). Features include WEP, WPA, and WPA2 encryption.

Of note, no warranty information is provided.