Please feel free to browse through these resources and download them for successful outcomes of your engagements in India:

Doing Business in India: This site is run by World Bank Doing Business Program. It has excellent information and contact numbers for doing business in India.
The Resource for New and Future Entrepreneurs: This site is an excellent resource for Startups and Entrepreneurs.
National Portal of India: As a national portal of India, this site has information on almost everything to do with/in India.
Foreign Investment in India - An Overview: This is an excellent presentation explaining three main regulatory categories of foreign investment in India, namely FDI, FII & FVCI. By Julie Hunt, Fulbright & Jaworski, L.L.P.
Investment Commission of India: This site provides excellent overview of investment opportunities in India in the areas of services, infrastructure and manufacturing.
India Commercial Country Guide: The Country Commercial Guide, by US Department of Commerce, provides a useful starting point for U.S. businesses pursuing export and investment opportunities in India.
Indian Ministry of Commerce: This GoI's ministry of commerce and industry site provides information for foreign trade with India.
India Brand Equity Foundation (IBEF): This non-profitable organization provides excellent information, reports and presentations on every business sector in India.