Servers

AlphaSpy
Free tool which allows monitoring of Half-Life or Half-Life mod servers on the net and quickly see vital statistics about the server.
http://users.bigpond.net.au/beredon/alphaspy/

Bob the Server
Dedicated Half-Life server.
http://www.bobtheserver.com/

Joe.to Servers
Includes several servers for Counter-Strike and Natural Selection, with news, forums, atciles, maps, and links.
http://www.joe.to/

Kalikops Headquarters
Multi-mod servers for Hunted, Day of Defeat, and Counter-Strike. With files, maps, IRC servers, pictures, and message boards.
http://www.kalikops.org/

UK Deathmatch Classic community
Dedicated Half-Life Deathmatch Classic servers. Features live players statistics, map downloads and forums.
http://www.zapper.org.uk