I'm not going to try to reinvent the wheel here.
Head over to Let's Play Math and Homeschool Math Blog for some great ideas for having fun with math.
A couple of recent favorite posts.
Free math resources (Check out the logic problems. I just love those!)
Coffee Shop (Ruth and I have spent a ridiculous amount of time on this game.)
Spend plenty of time at these blogs. They are so rich in information and fun. Enjoy!