On a current project the client supplied me with about 8 fonts, all of which were from a Mac. These were files with .lwfn and .ffil extensions.
After a bit of research I finally figured out how to convert these so I could use them on my development machine, which is Linux Mint 8. Linux Mint is awesome by the way. It's basically the current version of Ubuntu Linux but with all the media players, codecs, etc. included for you.
First I went to http://www.asy.com/sharecf.htm and downloaded their windows application 'CrossFont'. I keep a laptop around with Windows XP mainly for testing site in IE and for times like these when I need to install some conversion program and use on Windows. For some reason, I feel "icky" posting about Windows here and feel the need to explain myself....
Anyway, install CrossFont on Windows, then use it to convert your .iwfn and .ffil fonts to an OpenType/TrueType format.
Now copy those files over to your Linux machine and put them in your fonts folder.
sudo cp folder_where_your_fonts_are/* /usr/share/fonts/.
Then run the following to refresh the font cache