If you ever need a quick and short guide on web data sources that can be used (mostly) in any application to give it “top value”, this is the book for you.
This is a very short but loaded guide on available Data Sources with information on Websites, People, Locations, Companies, Books, Films… Overall, 57 different data sources are listed and categorized, and the author has also made a good effort pointing out the main drawbacks that a developer can face when using them (yes, Google has some restrictions too 
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Not many examples are provided though: here shortness is a premium over completeness. However, all the book is filled with links to the relevant web pages where more detailed information and examples can be found, so this is not a problem. Kudos to Pete Warden on this subject too!
How long these data sources might remain valid or available as stated might impact the book’s value, however as of now is a great and cheap acquisition that can be easily read on a weekend (or afternoon for the die-hards) and the next monday will start giving back its value.
One of those books that shouldn’t be kept too far from your development desk. It can be found here: http://oreilly.com/catalog/9781449303143/
