Windows only accepts TTF font files while Mac format’s their font into Dfont format. This tool by Peter Upfold lets you convert those beautiful Mac fonts into windows format. Then with your TTF fonts you can upload them to http://www.font2web.com/ or http://onlinefontconverter.com and make web fonts!
What to do about PostScript type files?
Say you thought you had a dfont file, dragged the file into the tool above and got an error saying it’s not the right format. Well, Looking more into the file you’ll probably find that you have a PostScript Type 1 file.
What I did was go to http://www.adobe.com/type/opentype/Type1-2-OpenType.pdf and find the OpenType format of the font you want to convert. Then go to somewhere like http://www.fontpalace.com/. There you can download your font in OTF format and it can be used everywhere.