Microsoft has released Windows Phone SDK 7.1 Release Candidate

The Windows Phone Software Development Kit (SDK) 7.1 provides you with all of the tools that you need to develop applications and games for both Windows Phone 7.0 and Windows Phone 7.5 devices. This download is the Release Candidate (RC) and provides a ‘Go Live’ license that enables you to develop and publish applications to the Windows Phone Marketplace.

The Windows Phone SDK includes the following

Windows Phone SDK 7.1 (RC)
Windows Phone Emulator (RC)
Windows Phone SDK 7.1 Assemblies (RC)
Silverlight 4 SDK and DRT
Windows Phone SDK 7.1 Extensions for XNA Game Studio 4.0
Microsoft Expression Blend SDK for Windows Phone 7
Microsoft Expression Blend SDK for Windows Phone OS 7.1
WCF Data Services Client for Window Phone
Microsoft Advertising SDK for Windows Phone

  Windows Phone SDK 7.1 Release Candidate