Son of Service (SOS) is a multiuser volunteer management database for non-profits. Useful for keeping track of work history, comments, reminders, skills, availability, and relationships, SOS requires PHP, a RDBMS, and a HTML 4.0 browser.
Installed and seems to work OK. But the functionality is quite limited. You can add a Volunteer, add skills and availability (days, hours). Then you can do reports on that. THAT'S IT. I see no way for a volunteer to actually log the hours they worked, or for any sort of task definition that might describe what the volunteer is expected to do. The description fields for the volunteer are quite extensive and customizable. Maybe that's the point of this app. If you can't manage your volunteers via Excel and email, then perhaps you will find this useful.