The Pew Trust has just released a new report on the development of online communities and their social impact on life in America. Of note: 90 million Americans have participated in online groups; 84% of 'net users have used an online group. A quote from the director: "For vast numbers of Americans, use of the Internet simultaneously expands their social worlds and connects them more deeply to the place where they live."

Here's the outline of the report. Full text is available online.

Summary of Findings
Table of Contents
Part 1: Background
Part 2: The Internet, Communities, and the Virtual "Third Place"
Part 3: New community participants
Part 4: The differences among online group members
Part 5: The Internet and local scene
Methodology

Online Communities: Networks that nurture long-distance relationships and local ties