The XeTeX project

XeTeX (by Jonathan Kew) is a successor to the shareware TeX/GX program for Macintoshes. It is a Unicode-based (UTF-8) TeX implementation which is able to make use of Mac OS X AAT (Apple Advanced Typography) .dfonts and OpenType fonts. It uses Apple’s Quartz system (which facilitates the afore-mentioned font access) to generate PDF output. XeTeX supports Unicode character sets and bidirectional typesetting, and is widely used by people studying linguistics, as well as an increasing range of people working in other fields.

A Linux and Unix-system version is available in TeX Live 2007; that version (of course) relies on OpenType fonts alone. A version is planned for MiKTeX version 2.7 (currently planned for December 2007).

The project has a web site for the user who wants more than this simple answer, and you can also sign up to a mailing list.

This question on the Web: http://www.tex.ac.uk/cgi-bin/texfaq2html?label=xetex