T-Mobile users who are part of the BlackBerry Beta Zone have reported getting notifications to sign up for the BlackBerry 6 beta testing for Bold 9700/9780 and Curve 3G devices. If you have any of those associated to your BlackBerry Beta Zone profile you'll want to check to see if you're eligible. A limited number of slots are currently open although, Research In Motion has not posted any version available for download as of yet.
We're gonna toss it out there that chances are it'll be a version or two behind what has leaked but if you're not down with using a leaked OS it's a good way to get BlackBerry 6 in an official manner. Who knows, maybe RIM will suprise us all and toss a version higher then what has been leaked thus far in there.
*UPDATE* - As noted and expected, it's OS 18.104.22.1688