Here's one that's very well known; I haven't used it in quite a while, but the site's still up...
R8 Receiver in Va.
Milair is certainly a challenge. There are no fixed scheds as such, and sometimes they use digital modes some of which we can't decode. I always point to the Worldwide Utility News and the Milcom list on qth.net as major sources on this kind of listening.
You also must understand something about how signals propagate so you know when and how to listen. The 2 very often go hand in hand; you can't hear the signal if propagation won't allow it.
Of course, I find it much easier if you have a programmable radio that you can build frequency lists; I use a TenTec RX320 and have heard lots of milair stuff, but once again, understanding when and where a signal propagates is very important. This is simply a personal opinion, but ham texts that prepare you for the test have basic theory in there, and that's where I would start. RadioIntel has several sites on the subject, but I have the feeling that they're a bit too technical for the casual person to understand.
73s and GL..Mike