The main page allows you to filter results by date range and region and then you can narrow your search with a number of options, one of them being "maps". The maps can be viewed in flash, with zoom control, and it is also possible to download a TIF image.
The map below is a 1507 world map that was first to depict the Western hemisphere with the Pacific Ocean as a distinct ocean (click on the image below to see the details). Check out the site if you're interested - looks like they have over 300 maps already online. Details about the project are available here, and it an associated Slashdot discussion here.