I have just finished reading my friend Antony Mayfield's book My Web Shadow. Antony has worked in PR and online reputation management for many years and knows more than most about how to track and manage the impression you make online. This book is ideal for people relatively new to the web and covers a wide range of situations in which you need to be aware of the consequences of your online actions. He has loads of tips on how to increase your positive online presence and wise words about what to do when things go wrong. Although it is aimed more at web newcomers than folks like me I still got a lot out of the book and picked up a few useful url's on the way.
[Disclosure Antony sent me a review copy of the book - but I'd have bought it anyway!]