Archive.org - downloadable pdf copies of out of print books, including volumes such as the Parker Society, REED, Visitation Articles and Injunctions of the Reformation, etc etc.
Biblegateway - searchable editions of the bible include the Wycliffe NT, the Authorised (King James) Version, the Vulgate, and scores of other editions in dozens of different languages.
Bodleian Library Broadside Ballads - over 30,000 ballads, ranging from the C16th to the C20th.
British History Online - digital library containing some of the core printed primary and secondary sources for the medieval and modern history of the British Isles
Canons and Decrees of the Council of Trent
CCEd - Clergy of the Church of England Database
Christian Classics Ethereal Library - large array of reformation-era texts available in full text.
Digital Library of Classic Protestant Texts - full text editions of religious texts from the reformation and post-reformation eras, brought together in a single fully-searchable database.
Earls Colne, Essex: Records of an English Village, 1375-1854
English Broadside Ballad Archive - contains more than 50% of extant C17th ballads.
John Foxe's The Acts and Monuments Online
Hanover Internet Archive of Texts and Documents - index to a wide range of key reformation documents online.
History Data Service - guide to a wide range of electronic data resources, principally in British social history.
H-Net - broad-based service for research in the humanities and social sciences.
Internet Modern History Sourcebook
ITER - gateway to the middle ages and renaissance.
Shakespeare Institute Virtual Manuscript Room - nineteenth- and twentith-century manuscripts, film scripts and theatrical prompt books relating to texts and performances of Shakespeare's plays.
Transcriptions of SP/12, State Papers Domestic, Elizabeth I
The Labyrinth - resources for medieval studies.