We have this book in the office, "Google Hack" I browsed a little. Quite informative and useful but I found out that even books about hacks does not put information that exploits legal issues.
Maximize searches, getting lyrics, Google maps - all this included in the book but not how to turn google into a.k.a Limewire and Napster. Try the search below in google.
-inurl:(htm|html|php) intitle:"index of" +"last modified" +"parent directory" +description +size +(wma|mp3) "Artist/Song name"
There are a lot of things you could exploit using google. I even read about an article that can get you usernames, passwords for certain accounts and even credit card numbers.. but be warned, all in this world follows the first law of alchemy, the law of equivalent exchange.