Wikipedia

People. Use Wikipedia.

Technically the site is an online interactive encyclopedia. In practice it acts as the beautiful Internet filter of information for information that we all so often need. It has its limits and tends to provide superficial information with links to more in depth information elsewhere, but the very existance and persistance of the site is a testament to human ingenuity. It works marvelously well. I highly recommend it. If you see an error, fix it. How many sources of information work so fluidly? Sure this means idiots could gum up the works, but there are scores of editors who make it their hobby to review recent changes and correct them if needed.

Example in practice: in order to find out which current countries were former USSR republics, I can go Wikipedia and quickly punch in USSR and get that information and more. Hard data. Quick and easy.

There are no advertisements either. It differs in that way from the standard encyclopedia sites that tend to try and provide limited information in hopes that the user will suscribe for more detailed information. Wikipedia, use it!