Jailbreaking your iOS device may be officially permitted under the DMCA, but that presumes there's a jailbreak out there to run. Happily, anyone with an iOS 3.1.2, 3.1.3, 4.0, 4.0.1 or iPad 3.2.1 device now has a super-straightforward way to jailbreak, thanks to comex's new JailBreakMe site.
Doing so is as easy as visiting http://jailbreakme.com/ on your iPhone, iPod touch or iPad and sliding the appropriate control. Right now the site is up and down as eager users attempt to access it, so you may be better off waiting a while.
Of course it's also worth remembering that, while the DMCA says it's okay, Apple says jailbreaking your device will nonetheless invalidate your warranty. As with any hack, attempt it at your own risk!