Wikipedia has loads of information but only if you want to get a basic overview of a topic to see if you’re headed in the right direction but that’s about all. Keep in mind that Wikipedia is user driven and not always accurate.
College level writing, whether it is for your papers or discussion board postings, should be supported by the research that can be found in scholarly sources.
Here are some sites to get you pointed in the right direction:
http://scholar.google.com (Scholarly Article search)
http://www.loc.gov/index.html (Library of Congress)
http://www.historians.org/pubs/free/journals/ (American Historical Association)