The official Google Earth Blog has lots of great tips and other info.

GE is one of my all time favorite programs. You'll get to know it pretty quickly. I can spend hours wandering the globe.

Some of my favorite features:

Historical images allows you to see older images.

User pictures gives you on ground views.

Turn on the 3d buildings layer to see models of important landmarks. Some places have recreations of ruins, the recreation of ancient Rome is really cool.

Google street view images are available as a layer, so you can get a ground view of what you are looking at. I use it to check out hotels I might to stay at or to familiarize myself with what a destination looks like before I hit the road.

Google Earth looks up, too. Click to Google Sky. Or Google Moon. Or Mars.

I overlay geologic maps onto terrain to get a 3d view.

Google earth uses two files: .kml and .kmz. These allow you to create information that others can view on their computer. These are getting more and more popular. Some local goverments provide kml files on their GIS web sites. My county provides many layers, including trails, bike routes, parks, etc. Very useful.

Get directions by right clicking on an object or placemark, click on directions from here. Then click on your destination and right click, directions to here, and away you go.

My magellin GPS software exports waypoints and tracks as .kmz. I enjoy taking our bike trips and plotting them into Earth. I have a whole folder of bike routes. Ski runs too.

I like it so much, I am seriously thinking of getting the paid Pro version. Pricey, but I can write it off for business. I'll get more features and better resolution. I've started to communicate geologic information with my clients using GE, which is convienient.

And don't get me started with how it interfaces with SketchUp. That's the program that is being used to create the 3d building models. It is also a free download with a paid pro version as well. Been a pro user for years now.

Oh, I've one more link for you ER. Have you seen Marine Traffic?

Have fun!