Think it takes a lot of time and planning to volunteer in a national park? Think again and join the Habitat Protectors of Yosemite (HaPY) at the weekly drop-in program. HaPY meets in front of the Valley Visitor Center every Friday between Memorial Day and Labor Day for a work session from 9 a.m. to noon.
http://www.examiner.com/x-4661-National-Parks-Travel-Examiner~y2009m6d12-Yosemite-National-Parkvolunteer-and-be-HaPY