Fact Checking Websites - http://www.makeuseof.com/tag/true-5-factchecking-websites/
Google Scholar, Snopes, Fact Check.org, WhoWhatWhen, and Merriam-Webster online dictionary.
Differences Between.net - http://www.differencebetween.net/
Website is searchable. There are broad topics such as as Miscellaneous, Technology, Objects, Science, Language, and Business. The broad topics all have drop down menus as well.
Virtual Reference Shelf - http://www.loc.gov/rr/askalib/virtualref.html
This is a product of the Library of Congress