The niche you are trying to fill would probably be appreciated by religious communities, especially parishioners in mainline protestant denominations and "emerg

The niche you are trying to fill would probably be appreciated by religious communities, especially parishioners in mainline protestant denominations and "emergent" Christians primarily concerned with social justice and human need. If you create a way for groups to specify a push community (food banks, shelters, non-profits in X niche) that would periodically receive a list of the group's available items, it would automate part of their mission. Religious communities would also be likely to post a link to you on their website and encourage participation internally. Outside of cities, this demographic is older and would likely be those already afraid of Craigslist for security reasons but savvy enough to see the benefit in your system.