Practically the source of all knowledge on the web, this encyclopaedia site is unbeatable for its breadth of coverage. Constantly being updated and expanded by a vibrant community from around the globe, Wikipedia boasts regional language sites to match. The moderation is more often than not top class and most articles are sufficiently correct to be extremely useful.

Entire days can be lost browsing Wikipedia, it is that interesting. It often doesn't cover specific practical subjects as well as it does popular culture but that can be attributed to a reflection of current society rather than a fault of Wikipedians. The fact that it never stops growing means that now, and for the foreseeable future, this will be the place to get information, not the huge books gathering dust on your shelf.