Fluxx is a commercially produced card game created by 
LooneyLabs. In Fluxx, almost every card you play changes the rules of the game, although these (fixed) cards are the only way in which the rules can be changed, so the game is not a true Nomic.
The Fluxx home page is at: http://www.wunderland.com/LooneyLabs/Fluxx/Fluxx.html