Australian Defense probably puts out the best images of any dept on the planet...

 

If you haven't then take the time to check out their image bank. 

Truly awesome.

The things they do with UAVs taking overhead shots and stuff is indescribably good.  The images of the troops in the field doing work and not looking like its a personal post for facebook or instagram is especially refreshing.

I focus mostly on their Army but the entire establishment is on the same page and puts out high quality pics for the world to see.

A first class shop in everyway.

I'd rank the Norwegians second, Russia third because they're all about letting you know what they're working on, and finally the US (can't decide between Canada...which is also good but has a smaller portfolio, the UK which is trending in the direction of US photojournalist...more instagram type pics, and Japan...I think its the language barrier that works against them the translations to English are just so awkward sometimes for 5th place).

Serious honorable mention goes to Turkey.  They're not higher because it comes from their defense manufacturers and not their DoD.  FNSS is a favorite...always will be they're awesome.  The other are prolific but the names seem to always be changing.