XGS for Windows -- Here it is... The compiled binaries for the Win95/98/NT version.
XGS for DOS -- The DOS version of XGS. Slightly less stable, but more robust (joystick support, speed throttling, multiple resolution support, PC<->GS exchange utilities, etc.) For playing games, this is my favorite version.
XGS for Mac -- I finally tracked down the last binary version of this. XGS for the Mac was probably the nicest of all the ports.
XGS for NeXT -- Stumbled across this one, too.
XGS source -- The good old source. This is the last version of the released code. The Linux port should compile fairly cleanly from this.
MS VC++ Source -- You need these files if you want to build the Windows version yourself.
GS ROM 01 -- The ROM that ran everything. I still have ROM 03 kicking around if anyone needs it... But why bother?