A transistor, you say? Pardon the noob-ness, but if I need multiple channels to operate each light independently, wouldn't a transistor not work? From my understanding (which is more than likely very wrong), isn't a transistor limited to a single throughput?
EDIT: A little more research dug this up:
http://www.ebay.com/itm/8-Channel-12V-Relay-Shield-Module-Arduino-ARM-PIC-AVR-DSP-SRD-12VDC-SL-C-New-/390369130004
Is that what I'm looking for?