Google Earth......what else is there?

I've had Google Earth for about a year now and whilst i'm sure i have'nt really used it to it's full potential, i wondered what other software of this kind there was available for download? Failing that, any suggestions for getting the most out of Google Earth? So far i've just messed about on it looking for the usual stuff.

Any recommendations? If this has already been discussed, please could you direct me to the thread?

Thanks,

CX.

There's a NASA project that's very similar but more geologically oriented. It's called "Earthwind" or something..