http://thesca.org/

The Student Conservation Association (SCA) is a nonprofit organization that offers conservation internships and summer trail crew opportunities to more than 4,000 people each year. SCA members complete projects in every conservation discipline - from archeology to zoology - and everything in between.

SCA is focused on developing conservation and community leaders while getting important work done on the land. Founded in 1957 to restore and protect Americas public lands and preserve them for future generations, SCA remains committed to this goal today.

SCA's mission is to build the next generation of conservation leaders and inspire lifelong stewardship of our environment and communities by engaging young people in hands-on service to the land. (less info)