Power Over Ethernet (a.k.a. PoE)
Using the extra wires in a CAT5 cable to carry DC to a device such as an AccessPoint.
Links
TerrySchmidt has a great description of PoE on NycWireless along with plans for building your own. http://www.nycwireless.net/poe/
Andy Freeman from GeelongWireless has made a PoE module for a 5.25inch drive bay. http://kawasaki.kz/wireless/poe.htm