I can't think of a better way to give back to communities, society, public welfare or the environment than by doing a volunteer vacation. I don't mean voluntarily taking unpaid days off (OK, those are often mental health days that we all need, but let's classify those as "personal care") but rather, vacations with a greater purpose where you volunteer for a cause while seeing the world.
Why bother? The benefits are immeasurable. You help a local community in need. You help scientists make progress. You gain insight into cultures and industries that would otherwise be hard to obtain. One of the most impressive volunteer vacations I've ever heard of was a co-worker going to Vietnam with a group to plant trees where landmines had formerly been. There are countless other ways to volunteer.
A friend of mine went on a couple of trips through Earthwatch, a non-profit that offers one-of-a-kind experiences where you do hands on field work to help sustain the environment. Hearing her stories inspired me. She went to Greece with a group of friends to preserve Greek ruins by documenting artifacts on an archaeological dig. Go her.
The idea stuck with me and I still plan to either go count butterflies in the mountains of Spain (I'm not making this up - scientists actually need this data to determine the health of a region's ecosystem) or help little baby turtles safely get to the ocean from their hatched egg on the beach (keeping animals of prey at bay).
Another friend of mine runs a non-profit that takes students to areas where social injustice has occurred to educate them on racial inequality via historical accounts by those who lived through them. Volunteers join her as escorts to help organize the group while on the road. Go them.
I volunteer for causes I believe in and donate money when I can. But I'm not surprised organizations have started soliciting volunteers to help fight noble causes on the ground or help with scientific research. And I'm not surprised that people are converting their hard-earned vacation time (and money) to improving society.
Globalization makes the world seem smaller (theoretically). And when the world shrinks, its needs become more real to us all.