For those not in the Android Beta Program, and you like to get a little dirty and manually flash your files, Android O Developer Preview 3 factory images are now available from Google.
Labeled as OPP3.170518.006, you can download these files for the Nexus 5X, Nexus 6P, Pixel, Pixel XL, Pixel C, and Nexus Player.
For instructions on how to flash a factory image, here you go. For instructions on how to flash an OTA .zip file, here you go.
We’ll flash ourselves and let you know of any big changes!