I was a math major from undergrad to doctorate, so obviously I think math is fun. Equally obvious to me (especially after teaching a variety of mathematical topics to college students), not everyone shares that opinion, which is too bad. Recently, though, I came across an organization devoted to making math fun for small children, and I wanted to share the link: Bedtime Math
Bedtime Math provides a variety of resources for introducing children to math in a fun way. The organization's name comes from the notion that a vignette with a math problem at its core makes a good bedtime story. They also encourage development of after-school math clubs, where kids can do fun activities with a mathematical theme.
If you are a parent of small children, and you want your kids to learn to enjoy mathematics, this seems to be a good starting point. There are books, videos and a daily math problem via email. There's even (shock!) an app for that.