For some of those in graduate school, you may not know how you are going to apply your research and leadership skills in your future career. Here is a suggestion. While you are inventing in the lab, keep up to date on the social implications of medical and life science research. It is not just big Pharma out there; other options do exist.
Listen to TED talks http://www.ted.com/ which showcase worldly "ideas worth spreading." Keep up to date on the social impact of science, such as organizations like Union of Concerned Scientists. http://www.ucsusa.org
Check out the Martha and Bill Gates Foundation. http://www.gatesfoundation.org
Learn about research agencies like the International Development Research Centre http://www.idrc.ca/EN/Pages/default.aspx and CIDA with programs such as the maternal and child health program. http://www.acdi-cida.gc.ca/acdi-cida/ACDI-CIDA.nsf/eng/FRA-127113657-MH7
One inspiring story is when a group of graduate students got together to design a baby warmer, to save premature babies in developing countries. http://embraceglobal.org/
Foundations like Edesia produce Plumpy'nut for famine relief. http://www.edesiaglobal.org
Read up on environmental issues. http://environmentaldefence.ca/
Find independent research and think tanks that you might want to intern or work for. www.aidsresearch.org, http://www.fraserinstitute.org/
Check out the founder of Genetic Alliance. She is inspirational. www.geneticalliance.org
Think outside the box, and develop a passion.
Follow-through with networking and internships, and you may end up working for your cause after graduate school or postdoc.
Good luck exploring the world!