Macintosh

BibDesk
A graphical BibTeX bibliography database manager for Mac OS X.
http://bibdesk.sourceforge.net/

Excalibur
A free spell checker designed for LaTeX documents
http://excalibur.sourceforge.net

iTeXMac
A text editor, a PDF viewer and a teTeX frontend. News, presentation, screen shots, download, FAQ, mailing lists and bug tracking.
http://itexmac.sourceforge.net/

LaTeXiT
A small freeware utility for typesetting LaTeX equations, without bothering with file creation, preambles, and so on, and exporting them as PDF.
http://www.apple.com/downloads/macosx/math_science/latexit.html

Mac OS X TeX Mailing List Archives
Indexed by date and thread.
http://w3.msi.vxu.se/~pku/MacOSX_TeX/

MacGhostView
A general purpose PostScript and PDF previewer based on Ghostscript. Presentation, news and download.
http://www.kiffe.com/macghostview.html

MacGSView
A graphical interface for Ghostscript, a PostScript previewer. Downloads.
http://pages.cs.wisc.edu/~ghost/macos/

TeXShop
Freeware GPL'ed graphical front-end for teTeX under Mac OS X. Documentation, installation instruictions, and download.
http://www.uoregon.edu/~koch/texshop/

XeTeX
A freeware typesetting system based on a merger of Donald Knuth's TeX system with Unicode and Mac OS X font technologies.
http://scripts.sil.org/cms/scripts/page.php?site_id=nrsi&id=xetex