GnuWin32

GnuWin32: "GnuWin32 provides Win32 (MS Windows 95 / 98 / ME / NT / 2000 / XP) ports of tools with a GNU or similar open source license. The ports are native ports, that is they rely only on libraries provided with any standard 32-bits MS-Windows operating system."
Summary
Packages Include:

• GNU utilities: bc, bison, chess, compface, cpio, coreutils (fileutils, sh-utils, stat, textutils), diffutils, doschk, ed, findutils, flex, gawk, gdbm, gcal, gengetopt, gettext, gperf, grep, groff, gsl, gzip, hello, help2man, iconv, jwhois, less, m4, miscfiles, patch, readline, regex, rx, sed, sharutils, tar, texinfo, tree, units, unrtf, wget, which
• Archivers and compressors: arc, arj, bsdtar, bzip2, gzip, lha, libarchive, unzip / zip, zlib
• Other utilities: byacc, cpuid, cygutils, file, ntfsprogs, openssl, pcre, popt, re2c, rpl, sgrep, tree, x86info
• Graphics packages: asciichart, compface, gd, jpeg, jbigkit, liburt, libungif, libpng and png utilities, libwmf, netpbm, piechart, plotutils, tiff, xpm, zimg
• Textprocessing- and postscript-related packages: a2ps, barcode, bm2font, deroff, dvidj, enscript, freetype, grap, gri, groff, indent, libxml, nenscript, pdflib, polyglotman, psutils, scribe2latex, src-highlite, t1lib, t1utils, troff2latex, ttf2pt1, unrtf
• Mathematical and statistical packages: bc, calc, crypt, fdlibm, gsl, units