It would appear that Google updated pagerank on Monday July 18th, 2011. This is likely a minor update or tweak to the Google Pagerank Update June 27th, 2011 we saw.
It is fairly common for Google to follow up with a few minor changes and I actually expected to see this happen. There were a lot of sites that Google updated on the 27th that seemed a little too good to be true. While there were a few others that dropped that I wouldn’t have expected.
Google.com dropped from a pr10 to a pr9 after the update on the 27th. And, now after this one they are back up to a pr10. I am sure they didn’t like seeing Facebook beating them for a little while with their pr10 to Google’s pr9.
Are they done tweaking and updating? Hard telling I have seen them follow up with just one little minor adjustment, and other times there seems to be several.
So once again if you are interested in Google Pagerank you might do some checking and exploring of your website.