I am seeing early signs of a possible Google update underway today. The WebmasterWorld thread started to get some chatter yesterday of people noticing shifts in the search results.
One WebmasterWorld senior member said, "Jez, something without doubt is happening. We've seen all the tell tale signs."
Another WebmasterWorld member said:
Is something brewing? I am getting a lot of foreign visitors hitting my site. Usually a sign of something in my recent experience. We are probably due a Penguin refresh perhaps.
Have you noticed major changes in your rankings and Google referrals yesterday?
Forum discussion at WebmasterWorld.