Google Maps for Android can now try to tell you what floor you are on and how to get to another location with the structure. Detailed floor plans are displayed when indoor map data is available for the structure. The list of locations with indoor maps is available here:
This list includes locations in the U.S. and Japan.
I could not find a way to look inside of a structure merely by pointing Google Maps for Android at it. It may be that you need to actually be in the building in order for the feature to activate. However, this seems very un-Google-like.