The Back Bumper - Jon Upton's highly entertaining and informative license plate collection site - (Make sure to check out his 2 Cents area.)
Ontario Plates - Need to buy a "Year of Manufacture" plate for your classic car?  THIS is the site to go to.
Road Map Collectors Association - An association which explores all aspects of road map collecting.
The King's Highway - Cameron Bever's History of Ontario's Highway's site.
Petrolmaps - A large, detailed, authoritative site by Ian Byrne about the history of oil company maps in Europe.
Pennsylvania Highways - Jeff Kitsko's site about the Commonwealth's roads.