Here are some resources that I've found useful in various teaching and/or research contexts:
Access to Archives is part of the UK archives network. The A2A database contains catalogues describing archives held locally in England and Wales and dating from the eighth century to the present day.
The Archives Hub provides a gateway to thousands of the UK’s richest archives. Representing over 220 institutions across the country, the Archives Hub is an effective way to discover unique and often little-known sources to support your research.
Attributions of Authorship in the Gentleman’s Magazine, 1731-1868 identifies 2,362 anonymous or pseudonymous authors of 25,585 letters, articles, reviews, poems, and other items in Georgian England's greatest magazine.
Beckfordiana: The William Beckford Website will aim to present current and earlier research, serve as a repository of facsimile editions of Beckford's works for easy access, and collect links to Beckfordian items on the web and elsewhere.
Bodleian Library Broadside Ballads: The Bodleian Library has unparalleled holdings of over 30,000 ballads, ranging from the 16th- to the 20th-Century. The Broadside Ballads project makes the digitised copies of the sheets and ballads available to the research community.
The British Book Trade Index is an index of the names and brief biographical details and trade details of people who worked in the book trade in England and Wales and who were trading by 1851. The National Library of Scotland maintains a separate Scottish Book Trade Index.
British History Online is the digital library containing some of the core printed primary and secondary sources for the medieval and modern history of the British Isles.
British Museum Collection Database: The entire database can be searched here and new records and images are added every week.
The Burney Centre: Selected texts by members of the Burney family are available online.
Chawton House Library Novels Online is an ongoing project making freely accessible full-text transcripts of some of the rarest works in the Chawton House Library collection of women’s writing in the period 1600 to 1830.
The Diary of Samuel Pepys contains the full text of his diary, along with several letters sent or received by Pepys, plus thousands of pages of further information about the people, places and things in his world.
Digital Defoe is a publicly accessible, subscription-free peer-reviewed journal and online forum which all those working in higher and secondary education, as well as those outside of academia, are welcome to join.
The Digital Miscellanies Index will create a freely available online database of the 1,000 poetic miscellanies published over the course of the eighteenth century.
Dissenting Academies Online consists of two fully searchable databases, Database and Encyclopedia and Virtual Library System, that will provide a comprehensive, archive-based history of the Protestant dissenting academies in Britain and overseas for a period of two hundred years.
Eigtheenth-Century Book Tracker provides a clearinghouse for students and scholars of the long eighteenth century to discover and share links to freely-available digital facsimiles of eighteenth-century texts.
The 18th-Century Common offers a public space for sharing the research of scholars who study eighteenth-century cultures with nonacademic readers, along with links to original texts, objects, and images, as well as resources for further reading.
18thConnect: Eighteenth-century Scholarship Online is an online finding aid and scholarly community in eighteenth-century literary and historical studies, peer-reviewing digital resources and offering a kind of table of contents to the best Internet resources in eighteenth-century studies.
Electronic Enlightenment (subscription) is the most wide-ranging online collection of edited correspondence of the early modern period, linking people across Europe, the Americas and Asia from the early 17th to the mid-19th century.
English Broadside Ballad Archive aims to archive all of the surviving ballads published during the heyday of the black-letter ornamental broadside ballad of the 17th century—estimated to stand at some 8,000 extant works—and make them fully accessible as texts, art, music, and cultural records.
The English Short Title Catalogue lists over 460,000 items published between 1473 and 1800, mainly but not exclusively in English, from the collections of the British Library and over 2,000 other libraries.
The Grub Street Project is a digital edition of eighteenth-century London. By mapping its print culture, literature, and trades, it aims to create both a historically accurate visualization of the city's commerce and communications, and a record of how its authors and artists portrayed it.
Horace Walpole’s Correspondence: browsable and searchable version of the Yale edition.
Internet Library of Early Journals s a digital library of 18th and 19th century journals, including substantial runs of the Gentleman's Magazine (1731-51), the Annual Register (1758-78), and Philosophical Transactions of the Royal Society (1757-77).
The History of Parliament consists of detailed studies of elections and electoral politics in each constituency, and of closely research accounts of the lives of everyone who was elected to Parliament between 1660 and 1832.
Jane Austen’s Fiction Manuscripts gathers together some 1100 pages of fiction written in Jane Austen’s own hand. Through digital reunification, it is now possible to access, read, and compare high quality images of original manuscripts whose material forms are scattered around the world.
The Jonathan Swift Archive, an electronic supplement to the in-progress Cambridge edition, makes available digitized texts of Swift’s prose works, transcribed from a variety of early printed editions.
The Lewis Walpole Library Digital Image Collection presents images of visual materials from Library's collection of English caricatures and political satirical prints from the late-seventeenth through the mid-nineteenth centuries.
Locating London’s Past allows users to search a wide body of digital resources relating to early modern and eighteenth-century London, and to map the results on to a fully GIS compliant version of John Rocque's 1746 map.
London Lives 1690 to 1800 makes available, in a fully digitised and searchable form, a wide range of primary sources about eighteenth-century London, with a particular focus on plebeian Londoners.
The London Stage, 1660-1800: a calendar of plays, entertainments & afterpieces, together with casts, box-receipts and contemporary comment. Compiled from the playbills, newspapers and theatrical diaries of the period.
The National Register of Archives contains information on the nature and location of manuscripts and historical records that relate to British history.
Old Bailey Online – The Proceedings of the Old Bailey, 1674-1913 is a fully searchable edition of the largest body of texts detailing the lives of non-elite people ever published, containing 197,745 criminal trials held at London's central criminal court.
The Nichols Archive Project is providing scholars with an analytical guide to the correspondence and collected papers of the Nichols family of printers and antiquaries between the time of John Nichols (1745-1826) and the death of his grandson, John Gough Nichols, in 1873.
The Poetry of the Gentleman's Magazine, 1731-1800 is an electronic database of titles, authors, and first lines designed to provide a comprehensive, fully browsable and searchable list of the 12,390 poems (4,775 are by identified authors) printed in the Gentleman’s Magazine to 1800.
Primary Sources on Copyright (1450-1900) is a digital archive of primary sources on copyright from the invention of the printing press (c. 1450) to the Berne Convention (1886) and beyond. See also the in-progress Register of Copyright Infringements Suits and Actions (c.1560-1800) .
The Reading Experience Database contains over 30,000 searchable records documenting the history of reading in Britain from 1450 to 1945. Evidence comes from published and unpublished sources such as diaries, commonplace books, memoirs, sociological surveys, and criminal court and prison records.
Representative Poetry Online is a web anthology of 4,800 poems in English and French by over 700 poets spanning 1400 years.
The Shaftesbury Project, which aims to produce a standard (printed) edition of Shaftesbury's works and correspondence, makes a selection of documents and textual material available on this web site.
The Thomas Gray Archive is a browsable, searchable and annotated digital archive of Gray's life and works, providing access to high quality primary sources and secondary materials and constituting a networked effort of institutions and individuals engaged in making the works available digitally.
The William Blake Archive contains electronic editions of many copies of Blake's 19 illuminated works in the context of full, up-to-date bibliographic information about each image, scrupulous "diplomatic" transcriptions of all texts, and a searchable electronic version of the standard printed edition.
William Godwin’s Diary is a digital edition (transcribed and scanned) of Godwin's diary, mappin radical intellectual and political life from 1788 to 1836 and providing extensive evidence on publishing relations, conversational coteries, artistic circles and theatrical production over the same period.
The Yale Digital Edition of the Works of Samuel Johnson presents all of Johnson's writings in the 21 volumes of the Yale Edition now in print.
Your Paintings (searchable) aims to show the entire UK national collection of oil paintings, the stories behind the paintings, and where to see them for real. It is made up of paintings from thousands of museums and other public institutions around the country.