BarCamp (one word) is probably best thought of as an idea that comes to life from time to time in different places rather than a specific place or organization. In contrast to traditional conferences where sessions are announced in advance and usually lead by experts; BarCamps, referred to as unconferences, are planned, scheduled and presented by the participants. The idea is to provide a place to share and learn. While participants may suggest a topic or prepare a presentation in advance, the actual scheduling is done at the beginning of the event, as participants write their presentations into available time slots and rooms. Generally presentations can be on any topic - technical, business, life skills, - and presenters do not have to be experts, only willing to share what they know or lead a discussion on a topic of interest. At the BarCamp I attended recently presentations included details of programming languages, cooking, slide rules, accessible web design, starting a business, maintaining a business while traveling out of the country, and much more. Some BarCamps are focused on a particular topic, for instance the ReBarCamps focus on real estate topics and the HealthBarCamp series focuses on health topics. While traditional conferences often encourage or require staying in expensive hotels (by their location if for no other reason), multi-day BarCamps traditionally involve camping.
The first BarCamp was in the San Francisco Bay area, inspired by the invitation only Friends of O'Reilly Camp (FooCamp) produced by Tim O'Reilly of O'Reilly publishing fame. The idea was to produce and unconference that is open to everyone. That openness has extended to publishing the formula for producing a BarCamp and allowing (and supporting) anyone who wants to to organize their own BarCamp. BarCamp also encourages openness in sharing the information and ideas from BarCamp. For instance, on the BarCamp.org site Tantek Çelik parodies the rules of Fight Club to produce the rules of BarCamp and the first rule and second rules of BarCamp are that you do talk about BarCamp and you do blog about BarCamp. Most BarCamps have a wiki where people are encouraged to share ideas prior to the event and notes, presentations, and photos during and after the event under open content licensing.
My first experience with a BarCamp was the BeaverBarCamp in Corvallis, Oregon. I stretched myself and gave a presentation on one of my hobbies, needlepoint. I learned a lot by presenting and surprisingly it was also fun. I also learned a lot at the various sessions I attended and met people and learned things that I found fascinating but likely would never have been exposed to otherwise. I'm looking forward to attending a BarCamp again in the future and would highly recommend participating in one if you have an opportunity.
You can find a list of upcoming BarCamps world wide on http://barcamp.org.
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