The Secular Student Alliance, or SSA, is a national group of free thinkers. I like their goals:
The mission of the Secular Student Alliance is to organize, unite, educate, and serve students and student communities that promote the ideals of scientific and critical inquiry, democracy, secularism, and human based ethics.
They are good folks trying to do good work... and they're having their annual meeting this year from August 7-9 in Ohio. Sadly, they have PZ Myers as their keynote speaker, but I suspect you can get past that and have a good time anyway.
As their name implies, they work with students to make them activists and leaders in the field. But even if you're an ex-student like me, you no doubt would get a lot out of the conference. So go check them out and attend if you can!