There are translators available to convert PC fonts into Mac format and vice versa, so you are not limited to sites that provide only fonts for your platform. One such program is TT-Convertor. Font Freak - Font Freak is one of the largest archives for downloading free true type fonts and dingbats for both PC and Mac. Plus Interviews with the designers. They have a list of Mac font sites too.
Every day there is a new font, and always a great smell.
A free font to download each week and a mind-bogglingly comprehensive links list. Brought to you by Mary Forrest, Fontmonger to the Masses. MacFonts - The premiere site for Mac fonts, and the most comprehensive list of Mac font sites on the Web. Includes other fonts resources as well. They also have dingbats and font tools.