They're called "aircraft landing lights" or ACLs, though they're also used on take-off for safety reasons and are supposed to be on whenever the aircraft is below 10,000 feet.

ACLs run on either 14 or 28 volts. The 14v kind can be used on a car with a few mods to its electrical system. It's illegal, of course, since they'll do a number on the vision of any driver coming the other way - but can come in handy once in a while if one is careful in using them, and are really good for getting revenge on a driver who tailgates you with his/her brights on. Here's a picture of how one guy decked out his old car with a few.