This is the top 10 from Alexa's ranking for India. I included 11, because thats Twitter!
1. Google India
google.co.in
Indian version of this popular search engine. Search the whole web or only webpages from India. Interfaces offered in English, Hindi, Bengali, Telugu, Marathi and Tamil.
2. Google
google.com
Enables users to search the Web, Usenet, and images. Features include PageRank, caching and translation of results, and an option to find similar pages. The company's focus is developing search technology.
3. Yahoo!
yahoo.com
Personalized content and search options. Chatrooms, free e-mail, clubs, and pager.
4. Orkut.co.in
orkut.co.in
orkut.co.in
5. Facebook
facebook.com
A social utility that connects people, to keep up with friends, upload photos, share links and videos.
6. YouTube
youtube.com
YouTube is a way to get your videos to the people who matter to you. Upload, tag and share your videos worldwide!
7. Blogger.com
blogger.com
Free, automated weblog publishing tool that sends updates to a site via FTP.
8. Rediff.com India Ltd.
rediff.com
Online portal with free e-mail and many other services.
9. Wikipedia
wikipedia.org
An online collaborative encyclopedia.
10. Indiatimes
indiatimes.com
Portal site; includes news stories under subject headings, and links to other information sources.
11. Twitter
twitter.com
Social networking and microblogging service utilising instant messaging, SMS or a web interface.