I have been wondering for a long time how to copy text out of gvim into the operating system/window manager's clipboard. Doing something unusual work today (most of my programming is a bash/screen/vim session; no gui until testing), I wondered again and finally decided to find out.
If you copy to the + register (i.e. "+, then a yank command) it will be available on the system's clipboard.
So now I know.