The Middle Persian script developed from the Aramaic script and became the official script of the Sassanian empire (224-651 AD). It changed little during the time it was in use, but around the 5th century AD, it spawned a number of new scripts, including the Psalter and Avestan scripts.
The Parthian script developed from the Aramaic script around the 2nd century BC and was used during the Parthian and early Sassanian periods of the Persian empire. The latest known inscription dates from 292 AD.
The Psalter script is a variant of the Persian script which was used mainly for writing on paper. It is known from fragments of a manuscript of the Psalms of David found in north-western China.
Parthian and Middle Persian written literature
http://www.artarena.force9.co.uk/parthlit.htm
Pahlavi literature
http://www.farvardyn.com/pahlavi.php
Free Pahlavi fonts
http://www.iranchamber.com/scripts/pahlavi_script.php
Circle of Ancient Iranian Studies at the School of Oriental and Asian Studies (SOAS), University of London: http://www.cais-soas.com
Ancient Berber, Arabic, Hebrew, Mandaic, Manichaean, Middle Persian, Nabataean, Parthian, Phoenician, Paleo-Hebrew, Proto-Sinaitic / Proto-Canaanite, Psalter, Punic, Sabaean, Samaritan, Sogdian, South Arabian, Syriac, Tifinagh, Ugaritic