The World Flying Disc Federation (WFDF) is the international body for all flying disc sports, including the sport of ultimate. They hold international competitions at all levels (they are currently hosting the U23 World Championships in Toronto and the World Overall Flying Disc Championships in Sweden). In addition, WFDF was recently granted provisional recognition by the International Olympic Committee (IOC). News release from the IOC is HERE.
They are also the international liason for Flying Disc competition at the World Games and wrote previews for each of the 6 teams attending (US, Japan, Canada, Great Britain, Colombia and Australia). The full previews (including more in depth analysis on each team) can be downloaded HERE.