The kids asked me to install a car mod on their Minecraft server. Now, I suck at Minecraft server administration (probably because I don't like or play the game myself), so here are some notes in case I need to reinstall this later.
The server needs to run CraftBukkit for this to work. In the server’s controlpanel I switched the Minecraft version to CraftBukkit 1.6.2-R1.0. (On another server I tried the same method with CraftBukkit 1.6.2-R0.1 and it worked there too. Not sure if earlier versions are supported.)