LSJ: Direct link to the LSJ through the TLG website.
http://stephanus.tlg.uci.edu/lsj/#eid=1&context=lsj
Lexicon to Herodotus: Direct link to the Lexicon to Herodotus through the TLG website
http://stephanus.tlg.uci.edu/powell/#eid=1&context=lsj
Lexicon of the Homeric dialect: Direct link to the Lexicon of the Homeric Dialect through the TLG website
http://stephanus.tlg.uci.edu/cunliffe/#eid=1&context=lsj
Perseus Project (Perseus Digital Library): The Perseus project is an attempt to make ancient texts accessible. Their focus is on Greek and Latin texts, but their collection extends to Arabic languages as well. Their collection includes texts in ancient languages in addition to links to philological information on the text and its English translation.
http://www.perseus.tufts.edu/hopper/
TLG (Thesarurus Linguae Graecae): The TLG is at base a digital collection of Greek texts from Homer to the fall of Byzantium in 1453. In addition to the digital texts, the TLG has digitized several Greek lexica, including the Liddell-Scott-Jones Greek-English Lexicon. A subscription is required to access the full corpus, but the TLG canon, the abridged TLG, and the Lexica are open access.
http://stephanus.tlg.uci.edu/index.php
PHI Classical Latin texts: This website is a collection of Latin texts, including a word search and concordance.
Corpus scriptorum Latinorum: This website is a digital library of Latin literature.
http://www.forumromanum.org/literature/
Vetus Latina: This site includes resources for the study of the Old Latin Bible.
L’Anée philologique: The goal of this database is to annually collect works of classical scholarship. It is published by the Societe Internationale de Bibliographie Classique in collaboration with the Society for Classical Studies. Note: This website requires a subscription.
http://www.annee-philologique.com/
TOCS-IN: This database provides the tables of contents for various classical journals and provides links to available online articles and abstracts. This project is comprised entirely of volunteers.
http://projects.chass.utoronto.ca/amphoras/tocs.html
The Vergil project: This project attempts to provide resources for readers of Virgil, including the Latin text, reading assistance, commentary, textual criticism, and translation.
http://vergil.classics.upenn.edu/
Gnomon: Gnomon is a searchable database of Classical bibliography. http://www.gnomon.ku-eichstaett.de/Gnomon/en/Gnomon.html
Project Dyabola: This site is an archaeological bibliography. http://www.dyabola.de/en/indexfrm.htm?page=http://www.dyabola.de/
Nestor: Nestor is a database of bibliography of the Aegean and related areas. New additions are made to the website with each monthly print issue.
http://classics.uc.edu/nestor/index.php/nestorbib
Zenon DAI: This is a database of bibliography which focuses on ancient archaeology.