Great post about Sea Turtle Conservation from The Vacation Gals blog. I'm a big believer in Volunteer Vacations, which by definition mean an immersion in a local community where you serve the needs of that community.
The idea of doing well by doing good is not new. Tikkun Olam, repairing the world, has far reaching effects. And travel can be one of the best roads to making this happen. The late Richard C. Holbrooke said "If you don't travel, you can forget that other people in other parts of the world are human beings too." (Conde Nast Traveler Feb. 2011, p. 16) The joy of volunteering in any area - be it domestic or internationally - is that you get back as much as you give. You get to know other cultures and broaden your own world view. You get connected at a very deep level. You get human.
There are wonderful organizations that organize volunteer and study trips: among them, Heifer International, where you can deliver animals to villages in need; and Toms Shoes - you can travel with Toms on a shoe drop.
There are countless opportunities, so I encourage you to follow your heart. And post your ideas here!