These are some fountain pen clubs that I’ve been able to find. If you have a club and want it listed please let me know. The only requirements are that you have a website (or something similar like a Facebook group where meetings are announced) and meet in person on a regular basis.
National: Fountain Pens Australia (Facebook) – see Facebook group for cities and times.
National: Fountain Pen Network – Philippines: Register for site to see the calendar
Arkansas – Little Rock: Arkansas Pen Club
Arizona – Tucson, AZ – Southern Arizona Pen Club
California – LA/Orange County. Southern California Pen Collectors Club
Georgia – Atlanta: North Atlanta Pen Posse
Georgia– Atlanta: Southeast Pen Collector’s Club
Massachusetts – Boston, MA: Boston Pen People
Maryland – Baltimore: Baltimore Fountain Pen Society
Michigan – Ann Arbor/Detroit: Michigan Pen Club
Minnesota – St. Paul: Pen Enthusiasts Northern Society
New York – New York City: Big Apple Pen Club. Note that the website itself hasn’t been updated in awhile, but the embedded Google calendar in the right sidebar has current meeting info. There’s also a Facebook Group
New York – Upstate NY: Greater New York Pen & Ink Group
North Carolina – Research Triangle area: Research Triangle Pen Club (That links to a MeetUp.com page for the group and all meetings are listed there. There’s also a website that has contact and other info)
Texas – Dallas: Dallas Pen Collectors
Washington – Seattle: Seattle Pen Club
Washington, DC – DC Metro Pen Club
Wisconsin – Appleton: Appleton Pen Club (Facebook) Also, Anderson Pens has recently been announcing meetings on their blog.