http://www.cstrike-planet.com/maps
Blow some minds with this.
Many of those were awesome (surely not any worse than the pos mappacks for killzone and cod), entirely new game modes were invented when people messed around with the map editor and settings.
When a game is successfull and the mod tools are there ,every morning is like christmas.
Battlefield was one of the kings when it came to modding (ironically bf3 will be riding on the coattails of those games while missing the thing that made it popular, sigh people chasing a carrot that no longer exists) and the giving from those games just never stopped.