Go
Introduction:
http://en.wikipedia.org/wiki/Go_(game)
http://de.wikipedia.org/wiki/Go_(Brettspiel)
http://www.dgob.de/einfuehrung/index.htm
http://playgo.to/interactive/
http://www.britgo.org/intro/intro2.html
Server:
http://www.dragongoserver.net/
http://www.gokgs.com/
http://www.pandanet.co.jp/English/
http://www.online-go.com/
Clients:
http://www.pandanet.co.jp/English/glgo/download.html
http://qgo.sourceforge.net/
http://www.rene-grothmann.de/jago/
http://www.gokgs.com/
Engines:
http://www.gnu.org/software/gnugo/gnugo.html
Knowledge:
http://gobase.org/
http://senseis.xmp.net/
http://www.egoban.org/
http://gobase.org/fuseki/
http://xmp.net/arno/fuseki.html
http://waterfire.us/joseki.htm
http://gobase.org/joseki/
Go Problems:
http://goproblems.com/
http://gogrinder.sourceforge.net/
http://www.u-go.net/uligo/
http://www.u-go.net/classic/
Misc Tools:
http://www.u-go.net/kombilo/
http://home.gna.org/quarry/
Online Shops:
http://www.gofigure.de/
http://www.hebsacker-verlag.de/
Information:
http://www.swissgo.org/
http://www.eurogofed.org/
http://www.nihonkiin.or.jp/index-e.htm
http://www.intgofed.org/
http://www.usgo.org/