These pages are now woefully outdated; I haven't updated the links in yonks. Still I resolved not to take the pages down, since there may still be some useful material in here. Just be prepared to be frustrated.
The following catalogue includes most of the electronic editions of eighteenth-century works publicly available on the network. "Eighteenth century" is understood extremely broadly — this very long eighteenth century runs from Milton through Byron, or thereabouts. All are available publicly from this page. Another class of texts is available by mail from the Oxford Text Archive. Note that libretti are catalogued on the Music page.