Here are some other great sites and resources on Ultimate:
Rules of Ultimate
The official rules of Ultimate Frisbee from USAUltimate.
World Flying Disc Federation
The WFDF hosts the Ultimate World Championships and is a full member of both Sportaccord and the International World Games Association.
Collection of videos from USAUltimate.
Ultimate history website.
Professional discs for Ultimate and other disc sports.
“How the Frisbee Took Flight”
An article on the origins of the Frisbee.