Online Map Libraries (Real World Cartography)

[Gallifreyan]

I don't think that this link was mentioned before in this thread, but the Barry Lawrence Ruderman Antique Maps Inc. website has many old maps. On the homepage it says that there are more than 10,000 15th-19th century maps.

There is also a site that is full of cartographic curiosities--strange real life maps.

[Xocatchil]

Here are beautiful maps of Belgium in 1777. The site is in french, but you only have to select a box on the map, and then on the blue link in "résultats" in the above part of the page.
It is not possible to download the map themselves, but only to view them (unless you want to pay 40 euros for a single map...).

http://www.ngi.be/FR/FR1-4-2-3.shtm