This is my first post here, and I'm not sure what the policy is regarding posting links to other sites. So I will refrain for now, and trust anyone interested is familiar with search engines.
The board game Hex was invented in 1942 by Piet Hein. You can see a picture at Wikipedia Hex: board game. It looks like a diamond shaped section of a honeycomb (regular hexagons.) The usual grid size is 11x11, but many prefer larger grids, even 19x19. The rules are very simple, but the game play can be very deep. There have been several online computer opponents, such as Queenbee and Hexilla. There are also decent free opponents to download such as Hexy (which runs under Windows) and Six (which uses KDE.) But the Benzene project produced two engines which blow all other silicon opponents away: Mohex and Wolve. They don't play at the strength of the best humans, but they play well, especially in the endgame. Mohex uses Monte Carlo simulation and is the strongest Hex engine AFAIK.
You can find a GUI to play against Mohex if you visit the Hex page on Boardgamegeek. Scroll down to the Files section, and click on "Modified Hex GUI for Linux." The instructions there will step you through downloading, editing, and building. There is no binary package for this game. It's tedious to set up, and if Six is good enough for you, then there's no need to bother. Development has stalled, possibly because the multiple threads option is buggy.
I don't know if this "package" is worthy of inclusion here, But I thought I'd mention it. Hex is an awesome game, if you're into that sort of thing.