Matt Cutts announced the launch of Penguin 2.1 in a tweet on Friday.  The new update will affect 1% of all Google searches. 

The first generation of Penguin was rolled out in April 2012, it's purpose was to target and remove webspam from the search results.  Sites with low quality backlinks and anchor text which was overly optimised were hit hard. 

In May 2013 Penguin 2.0 saw a complete change to the Penguin Algorithm.  Matt Cutts described how Penguin 2.0 improved upon the previous version.  "The previous iteration of Penguin would essentially only look at the home page of a site. The newer generation of Penguin goes much deeper and has a really big impact in certain small areas." 

At their fifteenth birthday event held at the Silicon Valley garage where Sergei Brin and Larry Page worked, Google revealed that it has been rolling out a new algorithm over the last month.

Codenamed Hummingbird, it replaces Caffeine as the engine behind the way user queries are interpreted and relevant search results returned.  The change affects 90% of searches.