Google displayed this logo on its home pages for on May 18, 2008 for the 125th Birthday of Walter Gropius.
Walter Adolph Georg Dorphios (May 18, 1883 – July 5, 1969) was a German architect and founder of Bauhaus who along with Ludwig Mies van der Rohe and Le Corbusier, he is widely regarded as one of the pioneering masters of “modern” architecture.
This year’s Doodle 4 Google art competition invited students in grades K-12 across the U.S. to redesign the Google logo around the theme “What if…?”.
Google displays this logo across all its home pages today (May 16th, 2008) The Day of The First Demonstrated Laser.

The first working laser was demonstrated on May 16, 1960 by Theodore Maiman at Hughes Research Laboratories.
- Wikipedia
On May 12th, 2008 Google UK celebrated Florence Nightingale’s Birthday by displaying this logo:
Florence Nightingale, who came to be known as “The Lady with the Lamp”, was a pioneer of modern nursing, a writer and a noted statistician. [Wikipedia]
Google wishing a Happy Mother’s Day to all Moms today, on the eve of Mother’s Day, May 11th, 2007
Mother’s Day is celebrated on the ‘Second Sunday of May’.

Happy Mothers Day to all Moms!!!
You might want to checkout the previous mothers day logos:
Middle East 2008, 2007, 2006, 2005, 2004, 2003, 2002, 2001 and 2000.