Newegg offers the TP-Link 300Mbps 802.11n Universal Wireless Range Extender for $15.99 with free shipping. (Amazon and Walmart charge the same via Prime and pickup, respectively.) That's the lowest price we could find by $4, although it was $1 less a year ago. It extends the range of wireless signals and features Ethernet, 64/128/152-bit WEP, WPA-PSK / WPA2-PSK encryptions, and five indicator lights.

Note: It's currently on backorder at Amazon.