Last night, in case you missed it, Microsoft once again pushed the big red button and bumped the latest Windows 10 Insider build for the fast ring to 14367. Just before that, the company also released a new SDK for the Windows 10 Anniversary Update, still in preview but now targeting builds 14366 and greater.
If you're a Windows Insider, you can log in and download the SDK, and begin to develop software for Windows 10, up to date (almost) for the coming Windows 10 Anniversary Update.
The preview SDK is designed to give developers an early look at what's coming, and should not be used for production development of current or near future Windows 10 apps. But for developers looking to gain an edge on the latest features coming in the Anniversary Update, this is the place to start.
You can download the latest bits from the developer section of the Windows Insider website (you'll need to sign in to the site with your Windows Insider credentials to get to the download. One note, there was an issue with the Desktop App Converter Preview (Project Centennial). It's fixed now, but you'll have to update it.