Microsoft has published yesterday an update for the Windows Phone SDK. This package contains an update for the current emulator, and a new one for the future Tango version of Windows Phone. Just a reminder, the Tango update will permit to have devices with less memory and features to get a very low cost than the high-end phones. So this emulator will allow you to test your applications for the 256MB Windows Phone devices.
This version does not contain the GO LIVE license, so it is forbidden to publish applications using this SDK!
Download the Windows Phone SDK 7.1.1 Update CTP.