MacTex

Finally, I found the solution for LaTeX on the Mac. I've been using MacTex for a month or so and it seems really solid. It has its own updater, the TeXLive utility, which allows you to keep your installation up to date. Your own local styles can be installed in ~/Library/texmf/tex/latex. BibTeX .bib files go in ~/Library/texmf/bibtex/bib or subfolders of this directory, and .bst files go in ~/Library/texmf/bibtex/bst or subfolders of this directory.

A system local texmf tree, which can be accessed by all users on a machine, can supposedly (untested by me) be placed in /usr/local/texlive/texmf-local.

This installation includes LaTeXiT, a utility I've mentioned before, that lets you easily produce PDF, EPS, TIFF, PNG, or JPEG files from LaTeX snippets. It can produce fully scalable PDFs with stroked fonts, for inclusin in presentations and posters. LaTeXiT also includes a LaTeX palette that allows you to select AMS symbols, operators, arrows, etc. from a graphical display.

LaTeXiT stores the LaTeX source within the PDF document it produces—if you want to edit your presentation later, just paste the PDF back into LaTeXiT and you can edit the source. Unfortunately, Keynote 5.0.1 doesn't seem able to access the LaTeXiT services, and LinkBack doesn't seem to work—but cut-and-paste isn't so hard.

The Grapher utility (in Applications/Utilities) also integrates with LaTex. Type a formula into Grapher, which provides a fairly intelligent wysiwyg interface (use ^ for exponents, / for fractions, "log" for log, "pi" for π, etc.). The arrow keys (all four of them) allow you to move around. Ctrl-(or right-)click on the selected equation will allow you to copy the LaTeX source for this equation (and it normally makes a better job of the latexography than I do).

texmf.local for Fink-installed latex

This note assumes you have a working Fink installation of tetex on your Mac.

To install the local latex classes, such as infletr, which produces letters on informatics letterheads (School, Institutes, Graduate School, ITO, etc.):

In a terminal window on your mac, do (don't type the % that is supposed to represent the shell prompt)
% cd /sw/etc/texmf.local/tex/
then the following
% sudo scp -r user@host.inf.ed.ac.uk:/usr/local/share/texmf/tex/latex .
Here user is your UUN, host is any dice machine you have access to. You will get asked for your mac password (for the sudo) and then, unless you have a valid Kerberos ticket, your dice password (for the scp access to your dice machine).
Then let the latex installation cache information about the classes you've installed.
% sudo texhash

Fink doesn't interfere with texmf.local, so you can use Fink to update your latex installation without destroying your copy of the informatics classes — but you should use rsync from time-to time to keep your copy up-to-date.

% sudo rsync -az --delete user@host.inf.ed.ac.uk:/usr/local/share/texmf/tex/latex /sw/etc/texmf.local/tex/latex
% sudo texhash

LATEX iT

\pi^2 =&6\sum_{i=0}^{\infty}\frac{1}{i^2}\\
\pi^4 =&90\sum_{j=0}^{\infty}\frac{1}{j^4}\\
\pi^6 =&960\sum_{k=0}^{\infty}\frac{1}{k^6}

This small app from Pierre Chatelier allows you to create JPG and PDF images for inclusion in your web pages, easily from L^AT_EX math. Here you see a jpg — click the image to see the pdf.

When you generate a pdf file, L^AT_EX iT embeds the L^AT_EX source in the pdf, so that,later, you can paste the pdf back into this application, and edit the source. Brilliant!