Everyone likes bling, so let's start this post off with some eye-candy (skip to 20s if you've got very little patience): That was pretty cool wasn't it? Even if you're not admitting it, I know you're thinking it. That was pretty damn cool. Lately, that video has been posted and reposted all over the internet.
Fifteen uncoupled simple pendulums of monotonically increasing lengths dance together to produce visual traveling waves, standing waves, beating, and (seemingly) random motion.