In April, the Text Creation Partnership released into the public domain over 2,000 eighteenth century works, in plain text. You can read more about this project and the texts on their blog:
Unfortunately, they didn’t make the texts easily accessible. To obtain them one had to apply by email to be subscribed to a Dropbox folder. There is a database and search interface, but it requires registration, and is unclear as to who qualifies for an account. I think that the database holds the marked up, XML texts, which have not (yet) been publicly released.
So I have created a package via the Open Knowledge Foundation’s Data Hub. You can download the zip package and an index in csv format from ckan. Note the zip bundle is around 142 mb. Don’t try this on dial-up. Check the index first. When I have time, I’ll work on a web interface that allows easy searching and sorting of it. I hope also that these texts will be made available individually, but given the number of them that’s not a trivial task.
Update: xml (.tei) and epub versions are available from tei-Oxford.
Update, 17/04/2016: the texts can now be found at Oxford Text Archive.