Google's home page has a hidden surprise - place your mouse cursor over the "Im Feeling Lucky" button and it will go for a spin.
Here is a video:
Depending on which one you click on, Google will take you to a specific type of search or a specific Google service.
Alex documented and Jerome where they go, including:
- I'm Feeling Doodly: random doodle
- I'm Feeling Playful: random interactive doodle
- I'm Feeling Artistic: random Google Art Project
- I'm Feeling Hungry: search for restaurants
- I'm Feeling Puzzled: random A Google A Day question
- I'm Feeling Trendy: Google Hot Trends
- I'm Feeling Stellar: image search for [orion+nebula]
- I'm Feeling Wonderful: random World Wonder Project
Forum discussion at Google+.