Windows – Convert .fon to TTF or OTF

TrueType fonts are supported directly on Mac OS X, as well as just about any other font type. If you double click on the font, it should open in Font Book, and you can just choose "Install Font".

I do recommend Validating the font first, since Windows fonts do not always include everything necessary to fully use the font, but there is no reason you should have to convert the font...

Per Adobe ( http://kb2.adobe.com/cps/327/327791.html as of 2009-11-11) Mac OS X supports the following font formats:

.dfont
Multiple Master (Mac OS X 10.2 and later only)
OpenType (.otf)   *
TrueType (.ttf)   *
True Type Collection (.ttc)
Type 1 (PostScript)  *

Which I believe is the majority of the popular font formats... The fonts flagged with an asterisk are also natively supported on Windows....

OTF is more likely to be a “better” font, as it supports more advanced typesetting features (smallcaps, alternates, ligatures and so on actually inside the font rather than in fiddly separate expert set fonts). It can also contain either spline (TTF-style) or Bezier (PostScript Type 1-style) curves, so hopefully you're getting the shapes the font was originally designed in and not a potentially-poorer-quality conversion.

On the other hand, if you're downloading free fonts from shovelware sites, you're unlikely to get any of that. Indeed, you may simple be getting a TTF font renamed to OTF.