This site gives the nutritional information of candy bars. If I find the lesson, I'll try to post it here later. Some sites are designed for interactive Math skills. Aunty Math is a story-style site with math challenges. Students can e-mail their solutions.
Past challenges are also available, so the site can be used without any interaction, if desired.
Ask Dr. Math is a collaborative site. B. E-mail penal projects and postcard projects can incorporate a lot of math. Estimating, graphing, comparing daily mail amounts, etc. etc. C. Flat Stanley, Traveling Ted, and Backpack Buddies are mostly social studies projects, but they can incorporate a lot of math.