I think nearly every game can teach you something that will help your poker skills, but very few of them can teach you a lot about poker, and that´s simply because poker is absurdly more complex than most games. Poker embraces the skills needed for chess, sc and wc, and still demands a lot of others. That´s why it is such an unique game.
Now, there is one game I know that really can help a lot with poker. I mean, A LOT. It is a very popular game in Brazil and in Spain (I think.. o.O). I´ve mentioned it before somewhere in the forums.. it´s called "Truco".
Almost everything you´ll find in poker is there: hand ranges, bluffs, slow playing, reading opponents, trapping, long and short term planning, tilting, trying to keep cool... and specially a whole lot of pattern recognition. That´s why it´s so useful to poker.
It is a very fast game and very, very fun to play. People play it a lot at parties, for example. Also, since it is a game played 2 vs 2, in partners, it requires a very sincronized sense of teamwork.
If you guys want, I can write a thread teaching it. It´s not so hard to learn, but it´s very difficult to master. Anyway, IMO it´s a perfect hobby for poker players, since it´s a fun way to spend time, playing it drunk with your friends, while still practicing poker skills.