Dumbbot is a Go program written by Kestrel in C which plays on KGS.
It's currently hovering around 30k on the server, but only because some people get fed up and resign to it ;-)
I guess it's about 35k - 40k at present. I hope to improve it a lot next week.
Dumbbot uses GNUGo in the final stage of play (specifically answering the "which stones are dead?" question from the kgsGtp wrapper). This 'assistance' doesn't affect its playing strength but does allow real people to play it easily. Knowing whether groups are really dead or not turns out to be quite hard to program. When Dumbbot gets better at this (and no longer needs GNUGo), it'll probably be at ~20k.