In Classics scholarship, titles of journals as well as Classical texts are often highly abbreviated.
A list of commonly used journal title abbreviations:
A list of common abbreviations for Classical authors and their texts:
The American Journal of Archaeology's guide to abbreviations:
Internet History Sourcebook: Ancient History from Fordham University
Perseus Collection: Greek and Roman Materials In Latin, Greek, and English translation.
digilibLT Late antique texts.
A selection of books which are either collections of excerpts of primary sources or books about primary sources on Roman civilization:
Here's a list of super useful books (not online) which are collections of translated excerpts in the library: