I'm currently in the process of making a race map for GMOD. This will be the first in a series of circuit-style race maps, but I also plan to add a few drag-strips on the one I'm currently making.
Here's a pic of what i have so far. I know its not much, but i started it 20 minutes ago.
They're really not maps that I plan to make largely public - just a bit of racing with my friends and anybody else here who wishes to join us.