Dragonlance, Ravenloft, Planescape, and Spelljammer (in that order), before WotC got a hold of them. Also 3pp for those settings (Dragonlance and Ravenloft during the 3e era.
Rokugan for Legend of the Five Rings also had a 3e era, started by WotC but continued by the original creator (much like 3e Dragonlance).
Middle-Earth (AiME and TOR 5e).
For sci-fi, there's a great 5e version of Star Wars out on the interwebs. And Mongoose put out a 3e version of Babylon 5. For that matter, there's a 3e Deadlands too.
I also second DCC.