Places to Play Go Online

https://go.mattle.online

http://www.gokgs.com/

http://boardspace.net/ (and other interesting games)

http://goshrine.com/

http://www.itsyourturn.com/

http://games.yahoo.com/

http://www.pandanet.co.jp/English/

http://www.dragongoserver.net/

http://www.361points.com/computergo/#gnugo (No registration necessary)

Places for Your Program to Play Go Online

http://www.gokgs.com/

http://cgos.boardspace.net/