ISO's are coming later today and The Windows 10 Anniversary Update will become available for users around the world in stages, as Microsoft needs to update more than 350 million devices.
Microsoft today released Windows 10 for PCs build 14393.10 to the Fast ring.
Build 14393.10 is the third cumulative update for 14393, which is the RTM build of the Windows 10 Anniversary Update. The Slow and Release Preview rings - and the Fast ring for Windows 10 Mobile - are still on 14393.5, which arrived just four days ago.
We're less than a day from the release of the Anniversary Update now, so this build isn't likely to make it to the Production ring in time.
Perhaps unsurprisingly, Microsoft released the new cumulative update without a corresponding changelog. Dona Sarkar has promised one soon, so stay tuned for that. Until then, we have no way of knowing what fixes are in KB3176929.
If you're on the Fast ring, you can grab the update by heading over to Settings -> Updates & security -> Windows Update -> Check for updates. If you're not, go to Advanced options and turn on Insider builds. Once your PC restarts, go back and set it to the Fast ring.
Update: Contrary to Dona Sarkar's tweet, it would appear that 14393.10 is going out to all rings - rather than just the Fast ring - including the Production ring, PCs running build 14393 but are not on the Insider Preview. Thanks to JayZJay for the tip!