I found a thread about Terraserver.com from about a year ago, but I didn't recognize many of the names, so I thought I'd bring it up again.
In case you don't know, this is a site with satellite images of most of the U.S. Of course the best part is that you can find coasters! I've discovered some really interesting things, such as:
-How huge the Beast really is. If the Beast station was where the PKI front gate is, the farthest point of the ride would be where the Beast station is now. You have to see it, it's incredible.
-Mean Streak is not shaped like an oval; it's more of a rounded triangle.
-You can really tell which rides were just thrown into parking lots, especially Shockwave and Viper at SFGAm.
-You can't see most of the steel coasters, but you can see their shadows!
Anyway, if you haven't heard of it, it's definitely worth spending a few minutes (or hours) on. Some parks you can search for, but for most, just type in the name of the town it's in (Kings Mills, Sandusky, Eureka, Doswell, Valencia) and zoom in.