On Wednesday 22nd May Google launched its latest update of the Penguin algorithm, which is known as Penguin 2.0. The update focuses on the linking profiles of sites and is designed to target spammy linking strategies. Penalising those sites which have spammy linking profiles within the eyes of the update.
Here is a link to Matt Cutts, head of Google’s Web Spam team personal blog announcing that the update has taken place. http://www.mattcutts.com/blog/penguin-2-0-rolled-out-today/
This update is said to be the biggest Penguin update to date and will affect around 2.3% of English searches. Here is some more information on the Penguin algorithm from both the Google webmaster blog and SearchEngineLand
The results of the update will be unclear for the next few days as the search engine settles down after the update. So in the next couple of days ranking fluctuations should be expected as the update is tweaked and more sites are hit by the update.