Hi Anil,
The book 'Linux Programming Interface' by Michael Kerrisk who is the Linux man-pages maintainer is full of useful examples and the breadth and depth of its coverage is remarkable.
When it comes to networking there is a book 'Linux Kernel Networking: Implementation and Theory' by Rami Rosen that is comprehensive and through.
It helps immensely once you understand the 'subsystems' first. This will help:
http://kernelnewbies.org/Documentation/SubsystemsThat being said if you truly want to 'understand' the kernel the best way is to start building your own and the best documentation I have found is the source itself :)