Internet Archive - THE online Library.

This is possible the most important site/initiative i have ever seen on the web.
Archiving not only websites constantly and continuously but also recording every book ever printed. Obviously they are still battling litigation issues surrounding copyright and again... I think this the most important initiative I have seen on the web.

Why ? to keep a record of exactly what the internet was doing at any given time in the past. tracking trends. cataloging information that so frequently comes and goes on websites, every website, every single page and picture. Then you have the realm of paper books.
Making sure that we have a digital copy of all of them. Taking that obscure 100 print book and making it available to every single person out there.

Apparently, about 3 qaurters of the worlds knowledge share isnt even on the net yet. \

Note from the archve.org website

"The Internet Archive is a 501(c)(3) non-profit that was founded to build an Internet library, with the purpose of offering permanent access for researchers, historians, and scholars to historical collections that exist in digital format. Founded in 1996 and located in the Presidio of San Francisco, the Archive has been receiving data donations from Alexa Internet and others. In late 1999, the organization started to grow to include more well-rounded collections. Now the Internet Archive includes texts, audio, moving images, and software as well as archived web pages in our collections."