FarsiWeb has released the first standard set of Unicode Persian fonts ever published, including Elham, Terafik, Terafik Bold, Titr, Roya, Roya Bold, Koodak, Nazli, Nazli Bold, and Homa (free download, version 0.4). The main advantage over legacy fonts is compliance with the Unicode, ISIRI 6219, and OpenType standards, and the addition of required but missing glyphs for Persian information processing. The fonts are highly recommended if you care for proper Persian display on your computers.
You can download version 0.4 of the standard Persian fonts from http://www.farsiweb.ir/font/farsifonts-0.4.zip.
An installation guide is avaiable here.
Some of the fonts are licensed under the GNU General Public License, which is both free software and open source. The remaining fonts will be released as free software as soon as they reach version 1.0.