This site, part of Roger Pearse’s Tertullian.org, serves as both an introduction to the history and iconography of Mithraism suitable for undergraduate instruction and an extensive collection of primary sources useful for original research. In particular, all references to the cult in classical literature have been assembled, when possible in English translation. Even more impressively, the “Catalogue of Monuments and Images,” based on Maarten Vermaseran’s 2 volume work Corpus Inscriptionum et Monumentorum Religionis Mithraicae (The Hague, 1956), provides images when available of the diverse material sources for Mithraism, from paintings to architectural plans (some of the photographs are by Pearse). This is supplemented by a list of recent discoveries and sometimes their associated images, including the London Mithraeum uncovered in 2013. Although there is no search functionality, when one knows what to look for, or just feels like browsing, this is an exceptionally useful and convenient site. There is also a fascinating section on Mithras items (in some cases their identity is uncertain) for sale on eBay and elsewhere.
http://www.tertullian.org/rpearse/mithras/display.php?page=main
