Encyclopedias are great sources of general information. They are the best place to start a research project or information search, especially if you need to build schema for your subject.
World Book Encyclopedia. There are four encyclopedias in one here and many articles are signed by the authors, who are experts in their fields. This information has a lot of authority.
Britannica School. Encyclopedia Britannica is better than ever and with four different levels for searching, it is just right for everyone from PreK-12th grade and beyond.