Google’s 2006 year-end Zeitgeist
It looks like the top searches in 2006 according to Google were:
bebo,myspace,world cup,metacafe,radioblog,wikipedia,video,rebelde,mininova, and wiki
According to their post, they do not create their list from search terms that popular overall because those terms are usually just generic words such as ‘ebay’, ‘dictionary’, ‘games’ e.t.c. Instead they look at the search items that are popular in 2006 and compare it to see how popular they were in 2005. If their popularity increased a lot from 2005 to 2006, those items are then included in the Google Zeitgeist
You can see their lists of popular search terms at:
http://www.google.com/intl/en/press/zeitgeist.html