Before the retreat, you may want to familiarize yourself with some of the major community based organizations by browsing their websites:
In addition to NAA and NIOST, the CBOWG website has posted research that members have done on various major CBOs on the Community Based Organizations Working Group homepage. Links to the synopsis for each CBO are on the bottom half of the page. Each synopsis lists important information about the CBO such as mission and reach. Take some time to familiarize yourself with a few of these organizations.
You may also find it helpful to read up on who's coming to the retreat by viewing the retreat participant bios.