http://www.techwench.com/windows-phone-7-jailbreak-tool-released/

Rafael Rivera, Chris Walsh and Long Zheng have developed ChevronWP7, the jailbreak tool for Windows Phone 7. It is an executable file that allows anyone to unlock a Windows Phone 7 device without a Marketplace developer account. With this jailbreak tool, users can install applications on their phones without going through Microsoft’s official Windows Marketplace.