Check out these Web sites for problem-solving activities:
Word Problems for Kids: http://www.stfx.ca/special/mathproblems/
MathStories.com: http://www.mathstories.com
DuPage Children’s Museum: http://www.dupagechildrensmuseum.org/
RHL School: http://www.rhlschool.com/math.htm
Problem of the Week: http://www.wits.ac.za/ssproule/pow.htm
Education Place: http://www.eduplace.com/math/brain/index.html
National Council for Teachers of Mathematics:
http://standards.nctm.org/document/chapter3/prob.htm
About Mathematics: http://math.about.com/cs/testprep/a/ps.htm