I am a German Go player, and have been playing (more or less) regularly for 7 years.
My grade is German 4D; but remember that I am unobjective, opinionated, and of course I win games only because of trick plays that are objectively bad :-) So, if you would take 9 handicap stones from me, but you think that I am writing complete non-sense somewhere in the library pages, it is probably you who is right!
Recently I got interested in improving GnuGo, a free Go playing program. If you want try it out, play against it on NNGS, or download it from the GnuGo Homepage (if you use Windows, look for the binaries listed there). Free means that everybody can use it, and everybody is invited to help improving it, and if you want to join, have look at the GnuGo development page. There is a lot to do!
Jeff: "Recently"? Looks like that comment is 6 years old! You still working that project? I just read a comment of yours on GoPlayingPrograms/Discussion (postmarked 2002 or earlier) that encouraged the reader to get involved with GNUGo. Thanks for the encouragement. :-) Please delete comment after reading it.
bugcat: The casual reader should note that the NNGS closed in 2005.