The Broer Map Library is a digital archive of scanned maps with heady ambitions — “to provide its collection of maps and atlases online in order to allow libraries and researchers who would not otherwise have access to such a large collection, have them available.” Founded in 2002, they claim a collection of 40,000 maps, with scanning apparently in progress and with plans to expand further. The ostensibly registration-only members’ section seems to be completely accessible; maps are in Zoomify format. Via Cartography.