Aventures - A mailing list for Parisian explorers.
Carrieres et Catacombes de Paris - Le Duc's excellent site features fantastic photo galleries of underground and topside items in Paris (in French).
Catacombes - History, pictures and maps of the catacombs (in French).
Catacombes et Carrieres de Paris - A great site with audio, video, virtual tours and tracts related to subterranean Paris (in French).
Catacombes et Vides de Carrieres - Resources related to catacombs and quarries under Paris (in French or English).
Catanaute - Nice-looking map-navigated site featuring a contest, silly girlie pictures, chat and a PDF tract.
Cataphiles.org - A female perspective on all things related to the Parisian catacombs (mostly in French).
Chateau Intrusion - Chronicles the adventures of a group of three French explorers in a variety of locations (in French).
Cube - Gorgeous but flash-only site of subterranean pics and a large-scale photomapping project (in French or English).
Cyberkata - Large site featuring many pictures and guides to subterranean Paris, includes forums (in French).
Dezafekt - Galleries related to urban exploration in France, mostly underground.
Entrailles de la Terre - A page of advice and photographs of catacombs and advice on taking photographs of catacombs (in French).
Experimental Building Urban Exploration - A minor page featuring pictures of waterworks and buildings in Bougival and Chevilly.
Friched.net - Beautiful photos of urban and industrial archeology.
Gargouille - Photo galleries related to catacombs, industrial sites, rooftops, caves and more (in French).
Geo1777 - A large site with lots of information about the history and geology of the catacombes (in French).
Gros Pipeau - A funny newspaper-style page with news related to subterranean Paris (in French).
KtaBreizh - Homepage of a Brittany-based group of catacomb explorers (in French).
L'Hermine - Catacombs in comic books, history, pictures (including 360 degree pictures) and maps of the catacombs (in French).
Les Stationes Fermee de Metro de Paris - A guide to the disused Metro stations under Paris (in French).
Maison de Bofil - Catacomb pictures and maps (in French).
Paris Sous Terre - Articles, an encyclopedia and a survival guide related to the Parisian catacombs (in French).
Paris Souterrain - Tunnels, catacombs, you know the drill (in French).
Site d'Hasan - Catacomb pictures, tracts, maps and even a an infrared catacomb webcam (in French).
Souterrains Creuse Par L'Homme - An academic look at underground haunts of various types (in French or English).
Titan's Catacomb Page - Advice, laws, maps, pictures and humour related to the Parisian catacombs (in French and English).
Underworlds - A photography-only site from across France.
Urban-exploration.com - Photo galleries related to underground and topside sites in France (in English).
URBEX -
Usines et Schrottrobbing - Photos of abandoned industrial locations around Strasbourg and the Rhine Valley (in French).
Uzines - Artsy-type black and white photos of industrial locations around Europe (in French).
Voyager Ailleurs - A collection of photographs related to catacombs and military and industrial ruins around France (in French).
Zedou-Connection - The design-laden site of a group of Parisian explorers, featuring hundreds of beautiful pictures and toys (in French).
Zone-Tour - Well-done site with pics and videos of tunnels, quarries and abandoned buildings in France (in English).