Here's more of them from the late 80's and early 90's. KGB/CIA/BND origins. Creepy (mp3 link).

That's absolutely fascinating.

In my alternate life, the one where I have more time to pursue interesting oddities, the world of short-wave radio is something I'd like to discover more about. There was one in my college's 24-hour library study space, and sometimes when working there in the wee hours, I'd take a short-wave break and listen to the oddest things from all over the world.

What you guys think of the Craigslist Numbers Stations? Legit or no?

Probably not. I'd go with Ryan Single's take on it (at the bottom of the article). I've never heard of the numbers files being accessible through the web (and especially craigslist), as it seems to be too easy, too 1920's spy-film. If the broadcasts are messages decodeable only by the person(s) that have the decrypt code, then they would be (at a guess) orders, movements, and general operations that may be undertaken by troops or spies. Nothing that you'd need or want hanging around, as after it's been broadcasted, there's no reason to keep a (semi) permanent record of it, and especially not on the web.
Note: I am not a spy, so I may be wrong. Just applying Occam's Razor to the whole thing.