I quite admire Dharmesh' networking skills, which is why I thought it would be only appropriate to ask this question on this forum.
Which as per you all is the best book on Business Networking (social networking), however not on line per se.
How to Win Friends and Influence People by Dale Carnegie
Never Eat Alone by Keith Ferrazzi
Networking with Millionaires by Thomas Stanley Some of the best advice on building relationships with highly approached busy successful business people.