the latest google beta
Google Maps, which returns map results from search queries (note the 'satellite' link at the top right which switches from maps to high-altitude satellite photos). Currently the service only covers the USA, although there are plans to extend the service later on.
I find it interesting to note that searching for 1600 Amphitheatre Parkway Mountain View CA 94043 turns up an intersection and not - as you might expect - a building. Trim it to 1600 Amphitheatre Parkway CA and it points to a large empty field a fair way up the road. Either Google doesn't want you to see their headquarters, or this system has some bugs to work out.
So, why is this different from other, existing satellite map searches? Well, let's be honest - it's been done by Google, so people noticed. Plus, it's web-based and doesn't need any software. But then it can give you directions on how to get to the location and where to buy pizza when you're there. Plus, you can search for a company's name and get the address, map and phone number all in one hit.
Not surprisingly, enquiring minds have already discovered that various military bases and other significant locations are blurred out; however they think they've spotted Air Force One and a certain facility in Langley, Virginia. Other nice pictures include the Golden Gate Bridge and Mt St Helens.