The world economy has collapsed. There is no internet or Wikipedia. How do you rebuild society?
CD3WD is a site built by programmer Alex Weir that's meant to help spur the improvement of the infrastructure of third world nations by giving them first-world technology and knowledge for free.
Everything from agriculture to technology is addressed in its roughly 4 DVDs worth of the archived information available online and for free in text and PDF format; it's also available to download in its entirety from this torrent.
Not only is this project a great information resource for third-world countries, but if you are of the survivalist mindset, this resource would be great to keep in your tool chest for possible use in the future if such a civilisation-ending disaster ever did occur. Think of it as a repository of some of the most useful human knowledge and technology.