Have you heard about the bus stop swing set that plays music? It's seriously amazing and I really want one. The mathematician in me gets all giddy thinking about the period of motion, harmonics, scale, etc that these play with. Check it out.
Ever seen a sand art video? Here's one of my favorites:
And here's a great song with its story told by toast.
I love OK Go. One of my other favorite videos by them is their Rube Goldberg Machine one. But here's another fabulous RG machine to watch and smile about:
And finally, a genius idea. I'm seriously thinking of having about a million of these printed up.