Great Reference Sights and Search Engines

These are some great reference websites and search engines which I utilize to obtain information I need I hope they can prove usefull to you too!
refdesk.com-This is a great site for current events that has many miscellaneous links that are actually usefull which makes it in my opinion one of the best reference websites. It even has a search engine that searches everything located on it to hopefully find what you need.
dogpile.com
wikipedia.com-free online encyclopedia
howstuffworks.com-You can search for explanations about how differenet systems,machines, and miscellaneous things work or function.