For relaxation I play Go, one of the few things I've shown any sign of aptitude for. I have also wasted considerable time trying to write a Go playing program since the early 1990s. As a confession that I have wasted so much time here here are some pages on my current effort.
LinkComment
BGABritish Go Association - I think I'm still a member
GoGoDVery useful collection of Go games
SGFSmart Game Format - file format for holding game records
Sensei's LibraryGood material here
GTPGo Transfer Protocol for communication between computer programs
SmartGoSmartGo is a Go program with nice features