An unconference is a participant-driven meeting. The term "unconference" has been applied, or self-applied, to a wide range of gatherings that try to avoid hierarchical aspects of a conventional conference, such as sponsored presentations and top-down organization.[1][2]
The term unconference refers to any loosely structured gathering that is distinguished from a formally organized conference (such as BloggerCon, an early unconference for bloggers).
But that changed in February when O'Grady arrived at Mashup Camp, an exclusive two-day gathering of Silicon Valley geeks billed as an "unconference." Attendance was free but limited to the first 300 people to sign up on the Mashup Camp wiki... Though the event had sponsors like Sun Microsystems, its agenda was created on the fly by attendees. As chaotic as that sounds, it sparked a ton of ideas.