Sauerbraten is played in two different leagues/ladders/tournaments:
The oldest existing one is PSL, which is now a monthly tournament. IN PSL there is a day to qualify (usually last Sunday of the month) in which everyone may participate who signed up for it previously. They provide a closed source binary to prevent cheats. Every First sunday of the month is the game of the current titleholder vs. the qualifier. Usually many people watch the games. Its a good way to see (and learn) how the best players play. It's a Sauerbraten classic, don't miss it ;-)
The other one is the well known ESL. They started in Spring 2009. They offer ladders mostly, but also tournaments every now and then. The stats/infos and social networking on their site is excellent. Many Sauerbrateners play it. So far they do not offer any anti-cheat binary.
Besides that some clans or communities have staged occasional games, like w00p ("fragfest") or sauerbratenfan.de.
