For those of you who, Heaven forbid again, may use another search engine and are blissfully unaware of these doodles, they are when on the day of an event, or anniversary of an event, Google will go all out and dedicate the most popular page on the internet to that day.
The most exciting of all are the interactive ones. You can play games or make a song, it is the most counterproductive yet exciting form of procrastination known to man.
Now if this isn't selling Google, I don't know what is.
Here are some of my personal favourites - Non googlers get ready to get your mind blown.

The day of the dead 2012

Winner of the Google for Doodle prize - India

Amelia Earhart's 115th Birthday

St. George's Day / The 30th Anniversary of the ZX Spectrum
And my favourite interactive ones
http://www.google.com/doodles/robert-moogs-78th-birthday
You will need a minimum time of 12.89 minutes to click on this link
http://www.google.com/doodles/79th-anniversary-of-the-first-drive-in-movie
Does the link give you a hint?
Yahoo say what?
-Tiger