Each Bike Safety Education class ends with a Community Ride through the surrounding neighborhood near Portland schools. They are always interested in having volunteers assist with those rides.
To sign up for the Bicycle Transportation Alliance's (BTA) Volunteer Listserv head to their website to sign up. You'll be able to specify what skills, interests and availability you can bring to the team.
The BTA staff and volunteers also maintain the fleet of bikes used for education classes and other rides or camps. Sign up for their Listserv if you have bike mechanic skills and a few free weekend days available during the year.