Geographically distant persons are also encouraged to participate in discussions on the mailing list or (if you're adventurous) you can form your own local chapter. You can sign up to the mailing list or read the archives here.
The "official" calendar of the Homebrew Mobile Phone club is hosted by Google at The Homebrew Mobile Phone Club Calendar Page.
There is currently no formal national or international membership organization, so starting a local chapter is as simple as finding a few interested people, deciding on a time and location for the meeting and showing up. A Homebrew Mobile Phone Club Frappr Group has been created to make it easier to find people with similar interests in your area.