The flag in front of every link tells you the language of a website. An X behind a link indicates Mac OS X specific information. New links will simply be added below the existing ones.
In case you know any other links that should be here please let me know.
Software
Gerben Wierdas teTeX distribution for OS X - you will need either the i-installer or the TeX-fat.dmg file 
CMacTeX - shareware TeX distribution including an editor
iTeXMac - an editor (especially interesting to users from central europe)
OzTeX - another (shareware) TeX distribution including an editor
TeXShop - an editor and viewer for LaTeX, PDF and DVI
BibDesk - a BibTeX bibliography manager
BiblioTeX - another BibTeX bibliography manager
Enhanced Carbon Emacs - Emacs editor for OS X
ScientificAssistant - Document Management and Scientific Wordprocessing System for MacOS X
Excalibur - a LaTeX-aware spelling checker supporting several languages
Equation Service - a program that uses pdfLaTeX to produce small PDF files containing equations and other text
IPAKeys - Keyboard Utility for better usage of IPA
jPicEdt - generates LaTeX, eepic and PsTricks code from a user-friendly graphical interface (Java) 
LaTeX Equation Editor - Typeset formulas for use with Keynote or other apps
PDFNupMaker - creates n-up PDFs (multiple pages on a single page)
TeXPower - Dynamic Online Presentations with LaTeX
JabRef - Java GUI for BibTeX and other bibliographies
Havea - LaTeX to HTML converter
Resources
Getting started with TeX on MacOS X - good Intro for Newbies, covers mostly technical aspects
MacOSX TeX/LaTeX Web Site - lots of useful information and home of the TeX on Mac OS X Mailing List
CTAN - the Comprehensive TeX Archive Network
Dante - CTAN in German
TeX FAQ - the UK List of TeX Frequently Asked Questions on the Web
Official TeX FAQ - maintained by Dante, answers many questions, yet it may be confusing for beginners
Unimac LaTeX - Swiss website especially for students with several tutorials
Cookbook for LaTeX - a good reference for working with LaTeX
Hypertext Help With LaTeX - this is a very useful online reference
Online Tutorials - brought to you by the Indian TeX Users Group
LaTeX en entreprise sur Mac OS X - LaTeX in French, for beginners, in businesses
LaTeX à portée de clic - French LaTeX tutorial
TeX Showcase - Examples on what can be done in (La)TeX
Das LaTeX Sündenregister - An article on outdated commands, packages and other mistakes
FAQ LaTeX - French LaTeX FAQ
Working with TIPA - About using the TIPA fonts wihtin LaTeX (aimed at Windows users)
Vaak gestelde vragen - Dutch LaTeX FAQ
FAQ about fonts - Version 2.1.5, August 14, 1996
Online Help - lots of info and tutorials (also much on bibliographys)
Geek Notes - a Mac OS X LaTeX Weblog
Jurawiki LaTeX - LaTeX for lawstudents (using a wiki)
BibTeX Styles - modified styles for German needs
LaTeX (LyX) Tips & Tricks - Lots of answers to possible problems using LaTeX
LyX on MAC OS X - Installation and some more info
Another LyX on MAC OS X site - Installation some more info
Schriften für TeX - Computer Modern Bright and LaTeX modfications for using Type-1 with LaTeX
LaTeX-Kurs Wintersemester 1995/96 - in 11 lessons
QNo's LaTeX Übersicht - Tutorial for modifying type-1 fonts for use with LaTeX
FAQ der Newsgroup pl.comp.dtp.tex.* - in Polish, of course
edoc - Dokumenten- und Publikationsserver der Humboldt-Uni zu Berlin - Guidelines for electronically archived publications (including a short but useful intro to LaTeX)
LaTeX-Generator - generates LaTeX templates with margins and headers/footers (uses KOMA); plus some links
TeX4u.de - Painless Intro to LaTeX
Installing Fonts for LaTeX on OS X - an excellent tutorial written by Bruno and Bob
TeX on Mac OS X - The most simple beginner's guide
Using LaTeX with other Applications
Using LaTeX formatted equations in Keynote - an article at macosxhints.com
Scripts for OmniOutliner to LaTeX
OmniOut2TeX.scpt - a script to convert OmniOutliner to TeX
OmniOut2pdfScreen - a script to convert OmniOutliner to TeX slides
Online Books
TeX by Topic - A TeXnician's Reference Making TeX work - an out of print verion on sourceforge
TeX on the Macintosh - chapter 15 of Making TeX work
LaTeX-Kurs - Textsatz und Layout mit LaTeX (1995)
LaTeX - eine Einführung und ein bißchen mehr... - Die Hobbits von der Fernuni Hagen
LaTeX für Fortgeschrittene - Neues von den Hobbits
Free e-texts on typography - a collection of books on various topics including typography, TeX and Postscript
Other Linkcollections
(La)TeX docs - well-sorted Linkpage
Really useful Links - standard site and some smaller pages
Huge link collection - maintained by David Craig
Einige WWW-Verweise zu TeX/LaTeX und verwandten Gebieten - Lots of useful links in German and English