Long Zheng, Rafael Rivera and Chris Walsh released ChevronWP7, a Windows Phone 7 unlocker.

This tool will allow you to deploy (sideload) any third-party Windows Phone 7 applications without requiring a Marketplace developer account. The unlocking process does not modify or damage your phone’s operating system in any way and can be easily reversed.

More information, and the download, can be found on the official ChevronWP7 group blog.