BarCamps are loosely structured conferences (also known as 'unconferences'), usually held for one or two days. See http://www.barcamp.org/ for more discussion of this approach to conferences.
/DC: A Washington DC-area Python BarCamp being planned for October or November 2008.
Texas Python Unconference, held on September 15-16 2007.
PyOhio: a daylong miniconference being planned for midsummer in Columbus, Ohio.