Leagues

Case's Ladder
Parent site for multiple competitions, includes links to leagues in specific games.
http://www.casesladder.com

ClanBase
Includes results and contact information for competing clans.
http://www.clanbase.com

Elite Clan Warfare
Playing spearhead, Call of Duty:United Offensive, and Counter-Strike:Source. Includes player/team statistics and downloads area.
http://www.eliteclanwarfare.com/

Multiplayer Games League
Playing Day of Defeat, Half life and Counter Strike series games. Includes past results and news.
http://www.mgleague.co.nz/

Online Gaming League
Includes forums, supported games list, and rules.
http://worldogl.com/

ProLeague
Counter-Strike series leagues organised by country. Prizes available.
http://www.proleague.org

QuakeCon
Annual event with multiple games. Forum and gallery of previous years.
http://www.quakecon.org/

Squad Games
Includes forums, downloads, results and fixtures.
http://www.squadgames.com/

Stronger than All
Includes results, fixtures, forums, and config files for download.
http://www.sta-league.org/

United Gaming Clans
Playing TFC and Counter-strike. Includes news, fixtures, results, forums, downloads and IRC chat.
http://www.ugcleague.com

WarLeagues
Includes gallery, downloads, forum and competitor information.
http://www.warleagues.com