-Panda / Farmer update (February 23, 2011) followed by more versions of panda with Panda 2.5 being the latest
-Caffeine update (June 8, 2010) with results effective from january 2011
-The very recent was the Google freshness algorithm (3 November 2011) which was focused on content that was relevant and recent.
Refer to this link for more on Google updates,
http://www.seomoz.org/google-algorithm-change