Basically my writeup is just to clarify between the two different groups in Fight Club (are they space monkeys or not?).
Members of Fight Club didn't have any titles -- they just went by their names. In other words, not all members of Fight Club are Space Monkeys.
To become a Space Monkey, Tyler would recruit members of Fight Club into Project Mayhem. At this point, they had were no longer referred to by name, and were simply referred to collectively as "Space Monkeys". If a Space Monkey died, he was no longer a member of Project Mayhem and as such was again referred to by name.
I don't actually recall directly hearing anybody call them Space Monkeys in the movie . There are only two references I can think of to this term. Tyler wipes the shaved heads of one of the members of Project Mayhem and proclaims, "Like a monkey ready to be shot off into space! Space Monkey!" (I am slightly deaf so I only recently heard him actually say "Space Monkey".) The second reference is a chapter on the DVD titled Space Monkeys, in which Tyler says the line mentioned above. The movie, however, is entirely consistent with the book in most respects (this one included). The definition of a Space Monkey does not change in the transition from paper to film, but Fincher leaves more to be inferred.
From the movie soundtrack by the Dust Brothers
jujuben23 informs me that the soundtrack has a song entitled Space Monkeys. Sure enough, track number 14 on Fight Club: Original Motion Picture Score is in fact titled Space Monkeys. Like all but the final Pixies song (Where is my mind?), i.e., all the songs by the Dust Brothers, this song falls somewhere between the techno and ambient genres, and has no vocal parts (I would say instrumental, but it's electronic music).