Maybe this site is old news to some but I was really impressed with the breadth of imagery and the fact that it is easy to find images of what you want. I found several images of LAVs, M2s, etc that I have NOT seen elsewhere (and believe me I have been looking).

Armor, Individual Weapons, Aircraft, Cannons, Ships and MORE... I had this site in my favorites...evidently I never bothered to take a look at it.

http://www.combatindex.com/

Like I say- it may be old news but I was impressed!