Damn, those Japanese kids get all the fun stuff.

Club Nintendo has opened in Japan. And it sounds alot like the Dreamcast Point Club, but only better. Here's the site, only in Japanese:
http://club.nintendo.jp/

Anyway, If you buy any Nintendo game with a recommended retail price between 3000 and 5000 yen (i.e. GBA games), you'll get 20 points. Anything higher (5000 to 7000 yen), and you get 30 points.

In addition to all this, club members are also ranked according to how many points they've racked up over the past year of membership. "Regular" members are those unlucky souls who earn less than 200 points a year. If you buy between 200 and 399 points' worth of games, you become a "Gold" member and receive a yearly "members-only original e-catalog disc" (demos, I'm assuming). Breaking the 400 mark makes you a "Platinum" member and gets you both the disc and one invitation a year to a Nintendo game exposition to try out new titles. All members get a free monthly email magazine.

More details can be found at the source: http://www.video-fenky.com/