Sure, everyone knows about washable markers. And permanent markers. Even fluorescent markers. But unless you trek into an office day after day, you probably don't often use dry-erase markers, those chunky pens with erasable ink. We had an old one on our phone message board that we rarely used until my back was turned one day, and Jake redecorated the front of our fridge. Cringing, I read the label: "for nonporous surfaces." Sure enough, it wiped right off. Hmm, I thought. Our sliding door could be like a giant erasable canvas.

I bought a package of eight nontoxic dry-erase markers at an office supply store (about $9) and gave them to my kids. In short order, the sliding glass door glowed with rainbows. Cleanup was easy--just wipe away the marker with a dry cloth. My one caveat: do not let your children try this activity on Plexiglas surfaces (it stains!), unless you're especially fond of stained glass.