This is all over the Internet already (see Google Maps Mania, El mapomóvil, Cartotalk, Ogle Earth, Tanto) but it looks like Google Maps has added detailed western European street data to its offerings. As c. spanring points out, the address finder does not yet seem to work. Countires now offering detailed road level data include Canada, United States, Germany, Czech, Netherlands, Luxembourg, Belgium, Italy, France, Spain, Portugal, Switzerland, United Kingdom, Ireland, Denmark, Norway, Sweden, Poland, Finland and Japan (and all those small European states tucked in between). Other countries such as Greece have spotty detailed coverage. Other countries such as Slovakia show some road network but do not seem to go down to street level detail.

Interestingly, there seems to be quite a bit of difference in what is offered in Japan (roads as well as contour lines and detailed drainage) than in the rest of the world. Road symbology also varies considerably between the the United Kingdom and Europe.