If all goes well this summer, I'll be off to SpiritFire near New Lebanon, New York. SpiritFire's Web site cogently explains what fire circles are. Here is a snippet from their Web :

So what kind of festival is SpiritFire? Is this a pagan festival?

SpiritFire is a retreat gathering, as opposed to a public or open-ended festival. We are non-denominational festival based upon music, dance, voice, art, and the many pathways that connect to them. We honor and welcome all paths, and recognize that in the circle, we are unified through our song and our joy. So the answer is, no, it's not a Pagan festival at all - but you'll find Pagans present, as well as Sufis, Buddhists, Hinduists, Yogis, Christians, Atheists, African traditionalists, and everything in between. You'll also find people who aren't following any particular path at all, and just enjoy the groove and friendly community of SpiritFire. So whatever your belief system, as long as you enjoy sharing sacred space with others around a fire with respect and an open mind, you are welcome!

Are SpiritFire circles "staged" performances, or can I drum and dance as I feel called?

Parts of the night-time rituals are pre-organized, such as the fire lighting each night. But the general course of the evening is meant to be a container in which you are encouraged to sing, recite poetry, dance and drum as your spirit calls. Every gathering has it's unique set of aesthetic and artisic agreements, and we try to make those things as explicit as possible via this FAQ and at the opening circle, or at meetings for drummers, etc. during the event. Both experienced and newer participants will all benefit by taking time during the night to breathe, view what is going on, and get a feel for how everyone is interacting with each other. You are welcome here, and we encourage you to ask questions of any of the staff or teachers. We only ask of each other that voices be honored and heard as each of us would want from our community, in a respectful and conscious way.

For more information:

http://spiritfirefestival.org/faq.php