Three more sites that I rate highly for modelers, wargamers and those interested in vehicle art:
Engines of the Red Army in WW2
The focus is on Soviet armour and vehicles, but includes many British, Canadian, and US lend-lease vehicles. The art work is superb.
http://www.o5m6.de/main.html
Engines of the Wehrmacht
Sister site of the above, but this is newer and a work in progress. So far it mostly has lorries and cars. Includes photos as well as art work.
http://www.german.o5m6.de/
Wings Palette
Aircraft only, but by far the largest and most detailed aircraft site I’ve seen, with camo schemes for most aircraft from WWI to modern:
http://wp.scn.ru/en/ww2/f
cheers,
Saxon