The Legermuseum literally means the Army Museum. The museum's admission is 5 Euros (as of 3/2004), and it's free to those with a Dutch museum card (a great investment if you'll be visiting a number of museums in the Netherlands).
It was oddly interesting, although I'm not sure I'd go back. To be honest, it was one of only a couple attractions open on Sundays, so that's what brought us there. On the ground floor, we were immediately immersed in a huge exhibition of modern weaponry, i.e. lots and lots of guns. The rest of the surprisingly large museum was impressive. They had lots of tanks, weapons, uniforms and just about anything else you can think of that's military-related. Also, they had a surprisingly educational and engaging separate exhibit space for children, mainly focused on medieval times with knights and castles and such. (I probably enjoyed this area more than the others intended for adults.)
The only down side was that most of the item descriptions were in Dutch without any English translations. My husband seemed to enjoy it, especially the temporary photography exhibit on Afghanistan. I found it intriguing, but in a slightly disturbing sort of way.