Wikipedia, an online source, but with unmonitored editing available by users. Please check all information through another verifiable source. An online encyclopedia, and good resource, even for math questions. However, it is a shared information source, so all entries can be changed by consumers. Therefore, all info should be backed up by another source.
fact monster - math flash cards for each grade level A great website for math flash cards for each grade level. You can choose
http://www.kidspace@IPL.org
http://www.homeworkhelp.com
http://www.homework@infoplease.com
http://www.math.com
This site requires a paid membership, but for $20 per year it is a great resourse for graphic organizers and extra worksheets especially for the primary grades http://www.enchantedlearning.com