I started off on YouTube searching for things like "weird google earth coordinates", looking for videos of weird/odd/bizarre/strange/alien Google Earth spots where the person had included the GPS coordinates. This is a major point, as (in most cases) just seeing a pic of something interesting isn't going to do any good. The exceptions are easily-described items, such as "huge pink rabbit in field". "Strange shape in desert", however, isn't going to cut it.
I then did the same on Google looking for GoogleMaps projects. There are a number of GoogleMaps pictorials around, usually of the "15 Strangest Spots on GoogleMaps" variety, with most of them repeating the same oddball stuff. On average, I gleaned as many new spots from the comments as the actual articles.
At one point I blundered my way across a site called Virtual Globetrotting, and while it was painstaking to skip past ten thousand celebrities' homes, it produced a few gems that I didn't see elsewhere.
The overall best site, by far, is GoogleEarthHacks. The hitch is that it takes user submissions, so you'll have to wade through a hundred "Airplane landing!" entries to find the real treasures spread throughout.
The official Google Earth forum is here. GoogleEarthHacks also has a forum.