SLIGE is an automatic level generator for DOOM and DOOM II. When you run SLIGE, you get a file that (after passing it through a blockmap generator like BSP) you can feed to DOOM (or DOOM II) to get a brand-new level that no one's ever played before. It runs in Windows95 and (I expect) Windows 98 and Windows NT, and I'm told it'll also run in Windows 3.1 with WIN32 installed, whatever that means. The source is also available, and it has been successfully compiled for DOS and Linux.