First there was Staffmen. (recently been revived, but more of a playstyle than a clan.)
Then there were Ninjas, based on the basic principle of Staffmen, just more elaborated. (been active more or less the whole time)
Then Guards and I think Knights of the Roses about the same time. *Rosewoods clan.
Templars also came about this time.
Mercs came later when Gnjus, Olwen and Oberyn decided to start a clan together.
Still lots of oldmy old friends playing this game actively.. proof that it is extremely addictive.