Talismans are equipped as weapons and can be used on either the right or left weapon slots. Pressing R1 or L1 (depending on which side the talisman is equipped) will cast the selected miracle. R2 or L2 produces a fast, but weak attack.
Below is a list of all the Talismans in Demon's Souls. Clicking on any of the names of the Talismans will give detailed information about that item on a separate page.