If you've never heard of Scribd, prepare yourself for a little bit of information overload. Scribd is currently the largest social publishing company in the world. More than 60 million people visit each month and can discover and share original writings and documents with each other. In existence since 2007, Scribd has quickly garnered attention for their great interface, excellent search and upload tools, and of course, the quality and sheer quantity of the content hosted.
It's also worth mentioning that I've found Scribd invaluable for finding several out of date, out of print books, perfectly scanned and available for free. In my opinion, if a tool or site can help you find something that no one else has been able to, there must be some value to it! Head on over and take a look, I'm sure that like me, you will be completely amazed and will quickly bookmark this fantastic site.