Un-conferences are participant driven self-organized conferences in contrast to tightly planned and top-down scheduled events. Foocamp, BarCamp, or CityCamp are some examples of un-conferences (see Wikipedia entry). They are ad-hoc events driven by the participants and their desire to share and learn through open discussion, demonstration and participation.
"NNIPCamp" was a series of concurrent sessions co-created by meeting participants. The purpose was to bring together a critical mass of people who are passionate about a particular topic and allow the creative juices to flow.
See the Sunlight Foundation's Unconference 101 for tips on participating in an unconference.