Volunteer / Internship / Lifetime involvement - You decide first. The rest is easy.
Physically a resident of USA but a heart that belongs to India. You can still do wonders. Meet your counterparts by joining AID, ASHA, or RIM. The opportunities are enormous.
Even your signature counts - you can help sign petitions and signature campaigns related to socio-economic development in India and matters of public interest. If an NRI in USA, then you may help by showing your support to Indian lobbying groups in US.
Want to make a career out of a lifetime involvement in social activities in India. Association for India's Development (AID-USA) can make it easy for you if you are dead serious.
A Clearinghouse (like an E-bay) for non-profit work, voluneerism, and compassion : You could be a person/organization that needs something, say a computer or funds or volunteers, and you can enter your request into the database. Or you could be a person who is willing to offer a used computer or volunteer your time, and you could list that too. You can also browse through complete lists of things that are needed or add your own.