This one was mentioned on the Classics list ... here's the blurb from Eisenbraun's:

Thesaurus Cultus et Rituum Antiquorum (ThesCRA) is a major multi-volume reference on all known aspects of Greek, Etruscan, and Roman cults and rituals. Providing both a sweeping overview and in-depth investigation, ThesCRA covers the period from Homeric times (1000 B.C.) to late Roman times (A.D. 400). A definitive work on the topic, ThesCRA is the culmination of many years of research by scholars from across the United States and Europe and throughout the Mediterranean world. Each of their texts-either in English, French, German, or Italian-is followed by a catalogue entry listing the epigraphical and literary sources cited and referencing ancient iconographical documents related to the topic. Many of these iconographical items are depicted either in line drawings in the texts or in the plate sections of each volume. On completion, ThesCRA will comprise five volumes, a book of abbreviations, and an index volume. The volumes are arranged thematically. The first three deal with dynamic elements of ancient cults, such as cultic ritual and practice, while the last two are devoted to static elements, such as cult places and their personnel.


The volume is rather pricey, but it definitely sounds like something useful. Further investigation shows the thing is being compiled by/is an outgrowth of the Lexicon Iconographum Mythologiae Classicae (similarly pricey, but similarly useful).