O’Reilly makes available 100 of their Google Hacks. They sorted them out in categories like Advanced Web, Images, News and Groups, Add-Ons and Gmail.
Most of the hacks are pretty basic stuff, for example hack 6 “Check Your Spelling”, and the explanation “Google sometimes takes the liberty of “correcting” what it perceives is a spelling error in your query” Not such a great hack if you ask me.
Most of the hacks published there are probably not hacks but advices. The advanced user should know most of them if he uses that services, so nothing new for us.
The new user has the chance to learn some new concepts, but he might receive the same level of insight from googles help pages.

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Doing some real google hacking
Google Real-Time Search