I haven't dont any volunteering, however, with my ecology class, I did some field work.  I measured aquatic insect diversity in two different streams.  Also measured tree diversity in a forest.
Heres the listing for the job I would like
Bivalve Nursery/Field Technician
Location: 
Company: .
Company URL: Not Entered
Salary: $25,000 - $40,000
Closing Date: Tuesday, February 15, 2005
Date Posted: Friday, January 14, 2005
Qualifications: 
Hard work, some heavy lifting, licensed diver, boating skills, work with tools and basic construction methods, aquaculture experience or strong desire
Description: 
Full time, Mon-Fri, along with alternating weekend 1/2 day. The work is in a bivalve hatchery, nursery and field location. Hard clam rearing, grading, systems maintenance. Also, work on species such as bay scallops, oysters and others.