WP7 Jailbroken, well not jailbroken, that's for iCrap phones. But the locked down os has been cracked open, enabling many more possibilities in the os.

"Windows Phone 7 is “finally” jailbroken! ChevronWP7, the unlocker tool, works with every WP7 phone and allows for the side loading of apps, the use of private APIs, and access to low level functionality. Basically, it unleashes your WP7 phone."

via Windows Phone 7 Gets Jailbroken | Gizmodo Australia.