MiKTeX – Typesetting Beautiful Documents
http://www.miktex.org/

MiKTeX is an up-to-date TeX implementation for the Windows operating system. TeX is a typesetting system written by Donald E. Knuth, who says that it is “intended for the creation of beautiful books – and especially for books that contain a lot of mathematics”. MiKTeX offers a complete set of utilities, macro packages and fonts.
MiKTeX (pronounced mick-tech) is an up-to-date implementation of TeX and related programs for Windows (all current variants) on x86 systems. MiKTeXs main features include: a) easy to install, b) complete: 1300 packages (fonts, macros, …) are included, c) living: packages are updated regularily, d) easy package management: missing packages can be installed automatically; a wizard helps you to keep your MiKTeX system up-to-date, e) fast previewing: the TeX output viewer Yap allows for an optimized edit-compile-view cycle (if the TeX authoring system in use supports source specials), and f) MiKTeX is open source. This has been added to World Wide Web Reference Subject Tracer™ Information Blog.