LibraryThing

This is a great tool for keeping track of your personal collection and you can sign up and catalogue up to 200 items for free. If you have more in your collection then the annual fee is extremely modest - $10 (US) per year or $25 (US) for life.

You can just use it to catalogue your own collections but you can also check for reviews or check under the Zeitgeist section to see what the rest of the world is reading.