Microsoft released Windows Phone 7.1 SDK tools yesterday, 28th September 2011. It's in RTW release, that means, it is released to web. Cliff Simpkins announced the release of the Windows Phone SDK 7.1 in Windows Team Blog.   In this post, find the link to download the RTW version of Windows Phone 7.1 SDK (Mango) which includes both the web and standalone offline installer for all separate languages.  

Download All Language Version – Web/Offline/Standalone Installer

Before installing the SDK, make sure to uninstall the previous Beta or RC version of the developer tools. More about the installation instructions and system requirements can be found in Microsoft Download Center. Find the below links to download the SDK:

Here is the list of non-English versions of the installer of WP7.1 SDK Tools: