I do wonder though, what the general political affiliations of the majority of people that volunteer for the peace corps or red cross in impoverished nations in say Africa (as an example) are. It seems like the few that I've talked to are definitely leaning more to the left.
It depends on how useful the groups are that people join.
"Peace activists", who help terrorists kill people, are usually from the left.
But the Dutch Christians who came to Israel in 2006 to help rebuilding after the war and then worked in charities for a year were more right-wing.
The guys that destroyed Africa's weak clothing industry with the "donate old cloths to Africans" were left-wingers, I think.
The founder of "doctors without borders" is a socialist but tends to be on the right side of socialism. (He was in favour of the liberation of Iraq and now serves in Sarkozy's government in France.)
Not every activism is actually useful and some that are are not "useful" in the sense they claim to be.
Here's a picture of a "peace activist" who wasted more than 500,000 dollars on finding out that the starving people in Gaza had not only enough food to feed the "peace activists" (who came to help Gaza without even enough food for themselves):
http://www.daylife.com/photo/02uy2JZ8Uw445/gaza
People in Africa are starving, but you will find the left-wing activists "helping" in an overstocked supermarket in one of the richest regions of the non-oiled Arab world complaining that neighbouring countries won't let her cross the border between two enemy states during a war.