Wargamer:

Grimm's Hangar
Zoogla's Zinnfiziert
Ton Weiss Figurines
Frederic Machu
German Wargaming Page
witchhunter.net
Back of Beyond Times
Darkest Africa

Manufacturer:

Pardulon
Pulp Figures
45 Adventures von Rattrap Productions
Wargames Foundry
Copplestone Castings
Artizan Designs
Anglian Miniatures
Old Glory Miniatures
Great War Miniatures
North Star Figures
Renegade Miniatures

Shops:

Empress Miniatures
Brigade Games
Miniaturicum
Battlefield Berlin
Planet Phantasy

Interesting stuff:

Landships WW1
WW1 Site
BBC History
WW1 Air Battles

Forums/News:

The Miniatures Page

Sweetwater Forum (German)