Dried pomegranate seeds are used in Indian and Iranian cooking. The seeds are collected from a wild, sour pomegranate rather than the sweeter pomegranate which is typically eaten fresh. The seeds are used to add a sour flavor to foods. Crush the seeds in a mortar and pestle before using. The seeds are also available ground but you'll get more flavor from grinding your own seeds
Find anardana (dried pomegranate seeds) in Indian grocery stores. You may also find them online at Amazon.com