Go Kibitz is a great place to discuss your Go games with other players from around the world. Free to sign up and use, upload a game you've played and join in on the conversation.
Play Go online for free! The Kiseido Go Server is where players from all over the world gather to enjoy the game of Go. You can find a game in no time.
Another great online Go server, Panda Net has been around for many, many years and is well known in the Go playing community. Play online for free!
The Online Go Server has a lot going on. There are tournaments, puzzles, and plenty of people playing fast paced games of Go. If you want to pick up a quick game, this is definitely the place.