Although membership to some groups may be restricted (e.g. some groups are for senior level executives), it is often worthwhile to check with the coordinators to see if there are upcoming events or other services that are open to non-members, or if they will let you serve as a volunteer or attend as a one-time guest.

For groups that are national in scope, the links below are to the national organizations. Look on the website to find the local chapter for the city/state/geographic area the interests you.