The following sources will help you gain background knowledge about a variety of World War II topics.
Choose reputable, reliable sources. Before you hit print, find out who authored/and or sponsored the web site. If you come across a student project, check out the bibliography to reach the actual sources used. Ask for help if you're unsure about the authority of a site.
Will your project focus on a local topic? Contact the following organizations for help.
The American Memory Collection is a massive deposit of primary sources. These collections might help you.