A new preview release of Android P is available now if you have a Pixel, Pixel XL, Pixel 2, or Pixel 2 XL. Today Google has announced Android P Beta 3, "an early release candidate build" which comes with "near-final system behaviors".
The official Android P APIs have been finalized with the previous beta, and this one seems to be all about bug fixes and minor improvements here and there. No major new features have been added this time around, but Google keeps on polishing the software ahead of its graduation from beta to stable - which will happen in August or September most likely.
System images are up for grabs if you want to manually flash your Pixel. If you've been running Beta 2 on your device, expect to see an over-the-air update notification in the next few days. If you haven't joined Google's Android Beta Program and want to do so now, head on over to this page. Once you enroll a supported device, it won't take long before you receive an OTA update that will install the latest beta.