Die Latex-styles von der Webseite sind jetzt auch als Installationspaket im self service verfügbar.

Interessant ist auch dieser Link: http://www.tug.org/mactex/faq/#qm05

QM.05 : Where do I put my personal additions to the texmf tree?

AM.05: They go in
~/Library/texmf
and various subdirectories structured according to the standard TeX conventions. Here ~/Library is the Library folder in your home directory. You may have to create the texmf folder, and any subfolders of it mentioned below. For instance, TeX will find any file in
~/Library/texmf/tex
or a subfolder of this folder, and LaTeX will find any file in
~/Library/texmf/tex/latex
or a subfolder of this folder. It is not necessary to run texhash when adding files to this local tree.
On Lion and above, the ~/Library folder is hidden. To open it, use the Finder’s Go menu and hold down the Option key to reveal an extra item in the menu.