I ran across this post on the Google Blog describing what makes a web design Googly. Here are Googles 10 design principles:

1. Focus on people—their lives, their work, their dreams.
2. Every millisecond counts.
3. Simplicity is powerful.
4. Engage beginners and attract experts.
5. Dare to innovate.
6. Design for the world.
7. Plan for today’s and tomorrow’s business.
8. Delight the eye without distracting the mind.
9. Be worthy of people’s trust.
10. Add a human touch.

Its hard to argue with this list. But as Google alludes to in their post, true success comes from the right balance of all ten. Something that always seems illusive when your in the thick of it, but extraordinarily simple when viewed after the fact.