Webmath is a math-help web site that generates answers to specific math questions and problems, as entered by a user, at any particular moment. The math answers are generated and displayed real-time, at the moment a web user types in their math problem and clicks "solve." In addition to the answers, Webmath also shows the student how to arrive at the answer.
This Halloween spider web activity for kids has some good Graph Theory and Geometry stuff! You can talk about the number of holes (vertices), how many times you go across (edges). And if your child decides to double up, what consequences does that have for the connections! ~Bon