The Windows Phone 8 SDK is now available for download here.
The updated Windows Phone Toolkit is available via NuGet here.
The updated Windows Phone Toolkit source and documentation is available on Codeplex here: http://phone.codeplex.com.
Windows Phone Dev Center Accounts $8 for 8 Days: Developers can register for a Window Phone Developer Account for $8 (regularly $99) for the next eight days. (Register at http://dev.windowsphone.com) If you have an MSDN subscription, be sure and use the Window Phone Dev Developer Account included with your subscription.
Windows Phone Developer Blog kick-off post here.
Watch Webcast: Windows Phone 8 Launch here.
Watch Build Keynotes and Sessions here.