There are hundreds of atheist, humanist, secular, freethinker, skeptic, etc. off-campus groups around the country. Off-campus groups come in a wider range shapes and sizes than our affiliates. Organizations like the Humanist Society of Greater Phoenix are incorporated nonprofits with their own buildings and a variety of programs. At the other end of the spectrum are interest-based meetups like Atheist/Agnostic Parents of Seattle or informal meetups like Omnipresent Atheists that meet regularly for drinks and conversation.
Many large compainies encourage employees to form special interest clubs. If your employer has an Employee Activities Union (or equivalent), look for a freethinkers' club. You might be pleasantly surprised.
Because of this, it can take a little effort to find a community near you. Googling a secular label or two (atheist, skeptic, humanist, freethought, etc.) and your city/state is a good way to start. Also, search Meetup and facebook for groups near you.
Off-campus groups can be affiliated with a number of national organizations, and each national maintains their own affiliate list. The United Coaltion of Reason, a national organzaition that promotes cooperation amongst local secular groups of all labels, is a great starting resource for finding local communities.
Secular Coalition for America
Traveling the world? Check out these resources to find secular groups abroad.