Random sites I've run across recently...
Next time you receive an email with a shocking "true" story, check Snopes, an index of urban legends and common fallacies. Do this before you forward it to your friends!
Project Gutenberg is a great source for public domain literature, offering over 20,0000 titles, including audiobooks. Speaking of audiobooks, LibriVox offers a collection of audiobooks read by volunteers, and anyone can volunteer (yes, even you or your students!).
The World Bank now offers a mashup of their data with Google maps - great for students researching countries or regions of the world. By clicking on an icon, you can see data for that country or region. Go to http://geo.worldbank.org/
Another clever mashup was created by high school teachers in California. GoogleLitTrips takes pieces of literature and maps locations in the book using GoogleEarth. Clicking on the various markers opens up more information and photographs about the locations. Better yet, it's customizable, so you and your students could contribute to the resources!
Enjoy!