The use of fog/driving light housings is popular among homebuilt systems. The lamps can be changed out for 20W lamps easily (which won't drain the battery as fast as the OEM 50-55W lamps). The lamps can be powered by a variety of battery sources such as a (relatively inexpensive) small sealed lead acid battery. Homebrew LED tail lights can be found at most automotive part stores, automotive part stores will provide a better selection of tail lights than WalMart. If you have any specific questions, fire away. That's what we geeks are here for.

My seriously geeked commuter bike: