I liked this dissection of Google Maps.

The interesting bits:
- they use PNGs with 8-bit alpha channels to make -really- nice transparent images that they can overlay on the maps.
- they have an XSLT processing engine—written in JavaScript of all things!—that converts XML location/POI data into HTML for display. Seems like a lot of extra work, but it is eXtensible I suppose.

I played with Maps some more tonight and I’m really impressed. The map dragging works really well. And I love the fact that I can expand my browser to full size and actually get a huge map. That is so beautiful.