I like collecting old maps. I like the stories they tell: how towns and cities have grown from tiny hamlets and fields.
Getting a selection of old maps online and geo-referenced is a bit of cartographic porn. Imagine my delight upon reading that The National Library of Scotland has released some 37,000 maps of Great Britain and selected other areas online and are rapidly working to geo-reference (show in the right place on an overlay) them.
(Found via oobrien.com)