It looks like there is an algorithm update taking place at Google search now - it is hard to say if it is Panda, Penguin or something unrelated - right now, it doesn't seem like Penguin but it might be Panda related. Google has not confirmed if there was an update yet but it does seem like something major touched down in the Google search results yesterday.
We have a lot of discussion and chatter around it at WebmasterWorld and all but one of the automated tracking tools showed significant changes.
Here are the automated tools charts for yesterday (click on them to go to their sites):
First reports of this change happened around yesterday morning where Pete Hall said, "Something happened in the UK overnight. Not really sure what to make of it - some verticals shifted quotes bit and others remain unchanged."
But then as the day went on and as people checked their analytics for the day's results, other webmasters started to notice:
Also seen fairly large movements here, seeing lots of huge names back which were knocked down a few months back.
Yes, I see some dance, not to much but noticeable, for me seems to be Panda related.
Even WebmasterWorld's moderator said:
Yes, there's some re-alignment going on, and i'm not sure it's finished just yet. Several SERPs showing wikipedia no longer the top, or near the top. Some may argue that's a good thing, but when it's a commercial site above it, it makes you think it's not yet settled.
Have you noticed changes? Do you think it is Panda related?
For the past updates, see our Google updates category.
Forum discussion at WebmasterWorld.
Update: Google's statement didn't tell us much:
Thanks for checking in -- as usual, we're continuing to make tweaks, but we don't have a specific "update" to announce.
Update #2: Google tells me this was not Panda or Penguin related.