The following logos appeared on the Google Homepage on October 31st of each year. It's interesting to see how their designers continue to find new ways to capture a recurring theme. For example, the most logical place to use a "round" pumpkin is as the "o's" in Google, but you'll notice they have strived to avoid this the past 3 years. It will be interesting to see if they can continue this creativity later this month.
For your own amusement, you can find additional holiday logos here.
Please Note: Google has requested that the above logos are only available for historic purposes and should not be used for daily use. Official Google logos which may be used on a daily basis are available here.