Journals TeX and LaTeX Packages: Includes packages for Acta Informatica, Archive for Mathematical Logic, Distributed Computing, Inventiones mathematicae, manuscripta mathematica, Mathematical Programming, Mathematische Annalen, Mathematische Zeitschrift, Numerische Mathematik, Probability Theory and Related Fields.
MusiXTeX: Created by Daniel Taupin, Ross Mitchell, and Andreas Egler, the package offers a set of macros and fonts that enables TeX to typeset music.
PSTricks: Access PostScript capabilities inside (La)TeX, by Timothy van Zandt. Site contains documentations, bugs list, and examples of application.
PSTricks.de: Unofficial FAQ with lots of examples, resources, and information about converting to PDF.
Xy-pic: A free package for typesetting graphs and diagrams in LaTeX, AMS-TeX and Plain TeX using the principle of logical composition of visual components. Presentation, samples and download.