Atlas Games		Current owner of Ars Magica. Atlas Games continues to actively support the game and produce supplements for Ars Magica (5th Edition).
Project Redcap		"Project Redcap is a Web site devoted to the tabletop role-playing game Ars Magica. Its goal is to provide links to as many Ars Magica-related resources as possible, in as many languages as possible." Project Redcap is effectively devoted only to the 4th and 5th Editions of Ars Magica. Some material may, however, be used by players of older versions.
David Chart's Ars Magica Page		Not much on these pages, but he is a major factor in Ars Magica.