Using an application, like CASA’s Image Cutter or the Automatic Tile Cutter, you can create your own map tiles for Google Maps. This means that you can replace image map tiles with any image tiles you like including other maps, or more importantly for designers and artist, replace them with portfolio images! How incredibly cool!
Click here for 5 examples of design portfolios using Google Maps. The above example is: Microtyp.org
(thank you Rhett)