Have mapped for Half-Life for several years. Mostly worked on the mod Action Half-Life, although most of my maps are also available for Half-Life DM. I have also done a DMC map, and had maps included in Action Half-Life and Vampire Slayer.
I started some Source mapping a few years ago and quit when Valve screwed up Hammer for 3 or 4 months via Steam (idiots). I'm going to start either Source or Unreal/Maya mapping as soon as I complete my current HL1 projects.