U/WIN is software that lets Unix programs be recompiled and run on Win32 systems: Windows 95-98-Me/NT-2000-XP. Descriptions, documents, downloads. http://www.research.att.com/sw/tools/uwin/
Implementation and subset of POSIX/Unix API for Win32 systems. Focus: efficiency, full platform coverage, with good support for low-end Win9x systems. Based on DJGPP runtime library by DJ Delorie. [Open Source, LGPL] http://pw32.sourceforge.net/
Toolkit suite of Unix and NT utilities for Windows, X Windows display environment, NutCracker development, interoperability, runtime environment. http://www.datafocus.com/
Recreates original Unix C shell and utilities fully from scratch, adds many enhancements, for Windows 95/98/Me/NT/2000/XP, OS/2. http://www.hamiltonlabs.com/cshell.htm