ArcData Online allows you to browse a world of geographic data to create live maps of specific areas of interest.
Maps can include a variety of information, such as floodplains, earthquake zones, and demographics.
This site is a great source of graphic representations of detailed data. The site is fairly fast loading, considering how much information is displayed in each map. Be sure to explore the site map to get an overview of what's available. ArcData allows the user to create a map from a specific data set. The user can then zoom in and out over particular areas of interest.