I've used several schemes over the years. At one point I had Inky, Pinky, Blinky, and Clyde.

Currently I'm using wooden roller coaster names. Raven, Thunderbolt, Phoenix, Cyclone, Tremors, Aska, and CBExpress (short for "Cornball Express", which would be a bit unwieldy a name for a computer ) My only real requirement is that it be a coaster I've actually ridden, but that leaves ~100 names available still (minus duplicates -- there's a bunch of "Cyclones" out there for instance)