Act locally, think globally. That's one of the premises behind Bryght VPS site, ChangeEverything.ca. Community members (anybody in the Vancouver and Victoria, BC area) on ChangeEverything.ca submit "changes" (things they would like to change in their lives and communities -- implemented as a custom content type using Drupal's content construction kit) no matter how large or how small and the community works together to help accomplish those goals.
ChangeEverything.ca is illustrative of an online community truism: after you have a solid and reliable technology infrastructure like Drupal to build an online community upon, the social i.e. the people part of the community matters more than the technology part.
And the people part is hard to do even if you have done this before. Accordingly, the Vancity team (the organization behind ChangeEverything.ca), led by William Azaroff, did some very smart things. First, they hired Social Signal who have oodles of online community experience to coordinate the site and community design. Second, Vancity hired Kate Dugas who administers and nurtures the ChangeEverything.ca Community with a deft hand.