[UPDATE] – Latest (3rd) penguin refresh pushed out 5 October
Weather report: Penguin data refresh coming today. 0.3% of English queries noticeably affected. Details: goo.gl/AF5kt— Matt Cutts (@mattcutts) October 5, 2012
[UPDATE] - NEWS (from Matt Cutts) 17 August 2012!
It's been a while since there has been any Penguin action but it sounds like we can expect an update soon.
At SES San Francisco Matt Cutts responded to the question asking about further Penguin updates by confirming that the engineers have been working hard and that the next release would include more signals with more noticeable impact.
[UPDATE] - Google Penguin 1.1 released 25/26 May 2012!
Intro - What is Google Penguin?
Penguin is the much anticipated Google algorithm update, aimed at addressing over optimisation, where site owners have gone a little to far to try and get their pages to rank well in search engines.
Matt Cutts, head webspam at Google stated that they were working on an update that would level the playing field in a Q&A at SXSW in March 2012.
And the idea is basically to try and level the playing ground a little bit. So all those people who have sort of been doing, for lack of a better word, "over optimization" or "overly" doing their SEO, compared to the people who are just making great content and trying to make a fantastic site, we want to sort of make that playing field a little bit more level.
A bit of background
There are possibly hundreds of on and off page factors that algorithms take into account to determine how a page ranks in search results. However, there are a few big factors that really made a difference, such as links and keywords. Not surprisingly, webmasters put a lot of effort in these areas so they could outrank their competitors resulting in, sometimes spammy results.
Google has continually tried to stay on top of these manipulations releasing at first monthly then more regular updates. Bigger updates were given code names and 2011 saw the start of the Panda updates. Panda seemed to work in a new way, running algorithms against the actual site, offline - penalising on a site-wide manner rather on a page by page basis. It was also the first update to have regular releases or refreshes. Penguin feels like a similar update, it seems highly likely there will be regular updates targeting various elements of over optimisation.