The Internet Classics Archive: Mainly Greco-Roman works (some Chinese and Persian), all in English translation.
Internet Library of Early Journals: Digitized 18th-19th century journals.
Luminarium: Medieval, Reniassance and 16th Century literary texts. Entries for each author include: works, biography, criticism, quotations and links.
Representative Poetry Online: Over 2,000 English poems by 310 poets from the early medieval period to the beginning of the twentieth century.
Sonnet Central: An archive of English sonnets, commentary, pictures, and relevant web links.
Turning the Pages on the Web: The British Library's digitized important historical works, including Caxton's Chaucer, Beowulf, Gutenberg Bible, Lindisfarne Gospels, Da Vinci's notebook, Sherborne Missal among others.
The Victorian Women Writers Project: Digital texts of Victorian women writers.
Also of interest: People with a History : an Online Guide to Lesbian, Gay, Bisexual and Trans History
All of these links have been added to JLS' Favourite Oddities & Curiosities