Like a lot of people, I think the new Google map service is really cool. I was reading up on how they did it and found a reference to a similar Swiss mapping site. The interesting difference here is that they use real satelite data and overlay the roads. If you search for Mürren, you can see the small town where my wife and I spent part of our vacation last autumn.
Google has aquired Keyhole, a company that does fantastic real-time 3D rendering of satellite images. Check out their impressive demos. I share the speculation about whether Google will combine the Keyhole images with Google Maps at some point. I think another zoom level (to "satellite") on Google's map would be cool... although perhaps not useful. :)
Another interesting online map is Map 24. They use a Java applet to give us a smoothly zooming map.