If you thought citing sources should wait to be taught in the middle school years, please think again. At the Yahooligans! Teacher Guides site, they have "developed guidelines for citing that are appropriate for the grade level and ability of your students." Here's their example of what a kindergartner and first grader should be able to gather and document from a Website.
It seems easy enough. My only argument is the skill needed to explain to a five year old what a Uniform Resource Locator means.