In addition to the standard theological bibliographic databases (ATLA Religion Database, Catholic Periodical & Literature Index, Index Religiosus), the following printed indexes/bibliographies and databases are of particular relevance for early church history.
Base d'Information Bibliographique en Patristique/Bibliographic Information Base in Patristics.
http://www.bibl.ulaval.ca/bd/bibp/english.html
A small (ca. 53,000 records), searchable online database for patristics from Laval University. Searchable only in French.
Biblia Patristica: Index des citations et allusions bibliques dans la literature patristique. 7 vols. + supplement. Paris: Editions du Centre National de la Recherche Scientifique. 1975-2000.
Ref. BR66.5 U53 1975
A comprehensive index of biblical citations and allusions in patristic literature, organized by biblical reference. Now freely available and searchable under the name BIBlindex (free but registration required). The online version adds ca. 100,000 references to the ca. 270,000 (some of which have been corrected) in the printed volumes. Authors and writings covered in the eight printed volumes include those from the beginning of Christianity up to and including Clement of Alexandria and Tertullian (vol. 1), writers of the third century except Origen (vol. 2), Origen (vol. 3), Eusebius of Caesarea, Cyril of Jerusalem, Epiphanius of Salamis (vol. 4), Basil of Caesarea, Gregory of Nazianzus, Gregory of Nyssa, Amphilochus of Iconium (vol. 5), Hilary of Poitiers, Ambrose of Milan, Ambrosiaster (vol. 6), Dionysius of Alexandria (vol. 7). The supplemental volume covers the Jewish writer, Philo of Alexandria. Authors included in the additional online references are Athanasius of Alexandria, John Chrysostom, Theodoret of Cyrus, Procopius of Gaza, and Jerome. Information for these authors is unverified and appears in red.
Bibliographia Internationalis Spiritualitatis. 1966-2006. (Publication suspended)
BX2350.2.B542
A comprehensive, topically organized annual bibligraphy on spirituality. Most relevant for patristics is Section 6 of each volume covering "Historia Spiritualitatis" including sections on "Primitiva," "Patristica," and "Periodus altera (s. IV-VII). There are also sections on the history of religious orders, including a section on monasticism, and on hagiography. There will be a certain amount of duplication with other bibliographies/indexes but this one is especially useful if your focus is on spirituality, asceticism, monasticism, etc.
Bibliographia Patristica. 1956-1997. 35 vols. in 23.
BR66.B524
This was the most exhaustive bibliography for patristics but was always slow in appearing, finally ceasing publication with the publication in 1997 of the volume covering books and periodicals from 1988-1990. See Robinson, Early Church, p. 3 (1.2); Kepple, Reference Works, p. 136 (BB6).
Bulletin de Théologie Ancienne et Médiévale. 1929-1996.
BR3.B85
The first four volumes (1929-1933) were published as part of the journal Recherches de Theologie Théologie Ancienne et Médiévale. Each volume consists of several fascicles appearing over several years. Indexes appear only after a volume is complete; without the index, the user must resort to browsing. All entries are abstracted; some of the abstracts amount to mini-reviews. See Kepple, Reference Works, p. 136 (BB7).
"Elenchus Bibliographicus" in Ephemerides Theologicae Lovanienses. 1924- .
BR1.A1E55
Superceded by the Index Religiosus (see above). The "Elenchus Bibliographicus" was published as the second of three annual issues of the journal Ephemerides Theologicae Lovanienses. A general theological index organized according to the categories of systematic (dogmatic) theology with a section on "Historia theologiae et theologorum" containing a sub-section on the patristic period ("Aetas patristica"). An "Index Historiae Theologiae" at the end of each issue listed names of historical figures; the first section of this index grouped patristic and medieval figures together.
Elenchus of Biblica. 1985-2011. Ref. BS410.B71 (preceded by Elenchus Bibliographicus Biblicus. 1920-1984.
Ref. BS410.B71
Primarily intended as an index for biblical studies but contains some material (especially on early Christian biblical exegesis) relevant for the patristics scholar. Ceased publication in 2011. See Kepple, Reference Works, p. 96f. (AA7-8).
Revue d'Histoire Ecclésiastique: Bibliographie. 1900- .
BX940.R5
Superceded by the Index Religiosus. The bibliographies appearing in every issue of this journal were the most comprehensive, ongoing bibliographies covering all eras of church history. See Kepple, Reference Works, p. 130 (BA7).