Project Pier is an open source "PHP application for managing tasks, projects and teams through an intuitive web interface" - it may also have some useful data model ideas for managing the tasks assigned to contacts
RailsCollab "is a free web based Project Management and Collaboration tool largely inspired by Basecamp, the communication-oriented project management solution from 37signals. Its roots come from a similar project called ProjectPier (previously known as ActiveCollab), which instead of Ruby is written in PHP."
The data structure for CiviCRM (slightly out of date), which is a popular FOSS CRM, is here. The top bit may provide some useful ideas in particular.
http://www.usability.gov/analyze/scenarios.html on Scenarios*
- Thanks to @MattDaniel
Relevant Employment/Volunteer sites
Plan Big - nice looking site, more focused on planning than volunteering - sponsored by banks
PloyMe - Casual Staff Recruitment Site
vinspired - UK young people volunteering site (16-25yr olds)
Help from Home - UK- 500 micro volunteering opportunities
Do Something : A not-for-profit organization - An article about DoSomething.org and SocialVibe
Software Platforms of Interest
Social Media Articles
10 Questions for Social Media Experts - may not agree with all of it.