Well this is quite a surprise! I just plugged in my Windows Phone to Zune in order to charge up the battery a bit, and low-and-behold an update to the Windows Phone Mango beta build is available! The update brings your developer provisioned Windows Phone up to build 7712 of the highly-anticipated Windows Phone update. While this is not the final RTM gold master version of Mango, it is pretty close.
The Windows Phone SDK also sees a refresh today with a few important points. All APIs are now locked so that what you build will work on all Windows Phones when they get the update. The emulater now has a nice screenshot capability and there is now a Marketplace Test Kit Release Candidate available for testing your XAP.