We are huge fans of Google Earth. Here are some great sites to get you started:
Google Earth Hacks
has a huge collection of files you can use with Google Earth (over
20,000 of them), as well as forums and other fun tools. They also have
a section where you can download Google Earth.
The Google Earth Blog is a very comprehensive unofficial blog all about Google Earth.
The Digital Earth Blog covers a variety of digital earth products (Google Earth, Google Maps, Microsoft's Virtual Earth, Nasa World Wind, etc).
The Keyhole BBS is the original message board for Google Earth, and it has hundreds of thousands of posts, making it a wonderful resource for information.
We hope that helps you as you begin your journey with Google Earth!