Via Declan Butler, The Macintosh Beta version of Google Earth is out. It works, but seems to lack the built in browser of the Windows verision though a reviewer says, "The interface is identical to the Windows version." A little while after I started using it, my mouse began to lag and I needed to restart the computer. But that may have been coincidence; I had a lot of other applications open.
See also Ogle Earth.
UPDATE: The built-in browser is there. The default preferences are just set a little differnt on t he Mac Beta.