newegg offers the refurbished Linksys by Cisco 802.11n Wireless 4-Port Router, model no. WRT120N, for $19.99 plus $1.99 for shipping. That's the lowest total price we could find for a refurb by $2, although we saw a refurb for $2 less in December (since expired). This router features four Ethernet ports and both WPA2 and WEP security.

Note that a 90-day warranty is included, however it's unclear who backs it.