Well, there's always my server. I am usually hosting my self-made Team Deathmatch build, and it usually is up every weekday from maybe 3pm-6pm, and usually 16 players full around 4pm-5pm.
It usually goes under a variety of names, lately: "IT'S THE FREAKIN' TDM!" but just look for the "Duckmeister's" in front of the name so that you know it's mine.
It's a lot of fun, has a lot of cool add-ons, and is well maintained and administrated.