Justeren made me aware of the super cool map24 java mapping applet. Enter any street name in Europe and a map will load with a host of interesting features:

• Infinite zoom, in as well as out, means you have a live continuous view of the world from a scale of "all of Europe" down to "My block"
  
• Continuous mapping. This is not a collection of maps but one large map of Europe
  
• Distance finder. Lets you plot a route on the map and calculates distance between any two points.
  
• Sleek look. Zooms are animated. The distance finder plots a radius from your last way point while you're picking the next way point
  

The distance measure correctly computes that my favourite walk north of Copenhagen is 12 km