You could also get fancy and do it by remote control.
433MHz Wireless RF Remote Control controller 4 Channel Learning Code Transmitter, $2.53 (free shipping), eBay: 253507623543
Pair that with this 433MHz 1Channel Wireless Relay RF Remote Control Switch Receiver, $3.29 (free shipping), eBay: 253597746316
Add a $2 12V power module and you have remote controlled lights for less than $10. The remote will support four receivers with independent control.