I've been mapping for Half-Life for several years, though not so much lately as I've been busy with work etc.
Action Half-Life is the mod I have been most involved with. One of my maps is in v1 of the mod, and I spent a lot of time behind the scenes beta-testing, fixing issues in other maps, and supporting other mappers in the scene. I also ran the AHL Map Deport for a couple years, writing reviews and digging up 'lost' maps to make them available.
As a mapper I tend to focus on visual effects, ambiance, and game play innovation. The HL1 engine is pretty limited, but that makes the challenge greater in a lot of ways when you want to do something different. I'm also big on customizing- most of my map .zips are big and have a ton of files because I always use custom textures, sounds, models etc. I tend to view each map as a mod unto itself, so I want them all to be very distinct.
I also DJ regularly, mostly electro-industrial & EBM. I am poking around at writing a fantasy novel, too.