Below are some general resources for finding sources for Ancient History. However, there are also dedicated sections for:
This website provides a plethora of ancient texts, many in the original languages, along with English Translations.
Fordham University provides a list of links to online primary sources from the classical era.
A website that offers academic and popular articles about the Ancient World.
An online academic database used by universities worldwide that is a superb resource for History students. To view full articles, you will require membership.
This searches internet sites for academic articles and books. It often only provides one or two pages, but it is often enough to find quotes and bibliographical details.