Here is a list of major organizations in this area, do let me know if there are others I should add here:

• http://www.wiproapplyingthoughtinschools.com/ – Azim Premji Foundation’s work with education.
• http://www.pratham.org/ – Pratham works in the area of education.
• http://www.aksharafoundation.org/about_us.html – Akshara foundation, Banglore-based, involved in primary education, is a part of Pratham Education Initiative.
• http://www.smilefoundationindia.org/aboutus.htm – Smile foundation, involved in health and education

And here are some directory of NGOs, not particularly good I must say:

• http://www.idealist.org/
• http://indianngos.com/

I will keep this list updated, and if you know of other major NGOs in the area or directories, do let me know.