The About.com article, ‘47 Alternatives to Wikipedia: 47 Websites You Can Use Instead of Wikipedia‘, indeed offers some great research Websites.  The article says:

‘Wikipedia is perhaps the most popular reference site online, with millions of high quality articles available on virtually any topic. However, there are limits to what Wikipedia can offer. Here are 47 Wikipedia alternatives you can use to find information, research a paper, get quick answers, and much more.’

Check out the list - http://websearch.about.com