The connection game Havannah is very similar to hex, it's also played on a hexagonal board, however the board is bigger and "6-sided", with sides typically beeing 10 cells wide. The goal is basically to connect 3 sides.
The game starts on an empty board. Players move in turn to place one stone on an empty cell.
The game is won by the first player to complete a ring or a bridge or a fork. All of these are 'chains': closed connections of one color.
Havannah is a strategic game. Not very much is currently known about the best strategy (compared to go). Some tactical structures are similar to hex.
...for the same reason as go: missing intuition especially during the first moves, to recognize influence & the direction of play; the unability to understand the meaning of a move and to see the strategic value of moves beyond the tactical horizon.
"The inventor has, in the summer 2002 issue of Abstract Games, put a $1000 prize money on a program that can beat him one out of ten (!!) games within the next decade."
One aspect of go is staying connected & to connect (during running/pushing fight, invading territory+break out). Whereas in go connecting is not the goal of game, just a means, in connection games it is the only goal.
You can also recognize virtual connections in a game of go, and during a practical game you often will have to check if they are really ones and can't be broken.
See also
Other Games Considered Unprogrammable
Connecting Techniques (in Go)
Connection Games
http://www.mindsports.net/Arena/Havannah/ excellent site; Tutorials+Server for Playing ("offline play")
(STATUS: Did work, but now the server seems to be down.)
http://141.57.11.163/havannah/online/ A simple java applet to play against each other (live) & a simple computer opponent
Both players have to press "Spiel starten" about at the same time (during 60 seconds). Wait a short moment. If it doesn't work reload the page containing the applet within the browser!
To arrange a game, use public chat on http://www.k2z.org (twixt-server) or
http://www.kurnik.pl/en (room hex) (I'm xurux!!)