I really like this Blog by Claire Beasley as it highlights some great ideas about how to start and grow your network, and how it can benefit you and those you network with. I am a serial networker with a fantastic 'little black book' and have derived great benefits - both personally and professionally - from those connections. In return, I have got great pleasure from helping people out where my skills and experience have been of use.
Oh - and Claire and I worked together as Floor Managers at M&S. You can work out how long we've been networked up!