I have a Google toolbar, so I rarely visit the Google homepage directly. I always regret missing out on Google's awesome logos! No more, I've found the index, you can see every Google logo that has ever been used (I think).
http://www.google.com/logos/index.html
Where do these logos come from? Can the average joe submit designs? I know Google has a staff member in charge of making logos, but surely he needs a break sometimes! Now I want to work on my very own Google logo. The trick will be making something that has never been made before. Off to the archives!
Weird trivia: I just finished looking at every Google logo ever. Slow day at work. Want to know something strange? The very first custom Google logo was not for a holiday or well-known event, but appears to have been for the Burning Man festival!