Brepols Latin Library, Series A (LLTA) is a searchable database of more than 32,000 Latin texts (Wake Forest University subscription)
The Latin Library contains the plain text of a great many of the extant Latin works.
The Perseus Project has the most widely read works from antiquity (both Greek and Latin) with accompanying translations and an interactive vocabulary and parsing tool.
The Chicago Perseus is a more streamlined version of the Perseus Project. It is less aesthetically pleasing, but faster and more reliable.
The Chicago Homer has the texts of ancient Greek epics with interlinear translations. It also sports a powerful search tool.