I love the iGoogle Moon Phase "gadget" by Aaron Hopkins. Every time I go to iGoogle which is my default website, I can easily catch up on the moon's current phase. It displays a realistic yet charming illustration of what the moon looks like, with a numerical percentage and description. Right now it is Waning Gibbous at 82% lit. This enables you to comment on the current moon phase and people are always impressed/shocked at your knowledge of natural systems.
Are there better rated moon phase "gadgets" out there for iGoogle? Probably. But this was the first one on the list to install, and I recommend it to you.