Jonathan Slocum and Winfred P. Lehmann (University of Texas at Austin), Old English Online [10 lessons with recordings; see also 'English Master Glossary' and 'Base Form Dictionary']
WebLearn: Showcase Old English [an e-learning website of Old English at the University of Oxford]
Old English Literature: A Hypertext Course Pack [a project launched by the English Faculty of the University of Oxford]
Old English Language and Literature [an extensive list of links to useful websites of Old English; maintained at the University of Connecticut Medieval Studies Program]
Woruldhord Project ['free online educational resources for the teaching and study of the Anglo-Saxons and Old English'; maintained at the University of Oxford]
Jeremy J. Smith (University of Glasgow), Essentials of Old English [available as smartphone application too]
Victoria Koivisto-Kokko (University College Cork), Old English Online ['The website is structured so that major grammatical concepts are covered in an individual module, which is subdivided into topics.']
Richard Zimmermann (University of Mancheter), Old Engli.sh: The Portal to the Language of the Anglo-Saxons ['offers study tools, news on current linguistic research and resource development, a link directory, text editions, trivia articles and more'; Cf. The Old-Engli.sh Dictionary, 'a free, comprehensive, accurate and easily searchable Old English to Modern English dictionary']
Old English Resources ['This is a project for collecting and organizing Old English resources.... The community can submit resources to be added to the list through a form that links to github.']
English 475 ― Old English [Materials for the OE class by Edwin Duncan (Towson University)]
Learning Old English [by Tony Jebson]
An Anglo-Saxon (Old English) Subject Reader
The Historical Grammar of the Old English Language
ASNC Spoken Word, Old English – Grammar Exercises
Michael D. C. Drout (Wheaton College), King Alfred's Grammar [also available here]
Introduction to Old English Language and Literature [maintained by Kevin Kiernan (University of Kentucky)]
Daniel Paul O'Donnell's page on Tutorials [contains many materials on Old English]
An Anglo-Saxon Reader [an electronic edition of the same title by James W. Bright, published in 1912]
Germanic Languages: Conjugate Old English Verbs [Enter the infinitival form of an Old English verb, and its full inflectional paradigm is provided.]
Omniglot: Old English/Anglo-Saxon (Englisch) [Explains the Old English alphabet and runes]
Notes and Translations [a website by Jonathan A. Glenn (University of Central Arkansas); offers modern English translations and notes to some Old English poems]
Aaron K. Hostetter (Rutgers University Camden), Old English Poetry project ['Translations of almost 79% of all extant Old English poetry can be found here.']
Swarthmore College, Department of English Literature, Old English Riddles ['These riddle exercises were developed for use by beginning students of Old English.']
Beowulf Resources [a comprehensive introductory page formerly from the Reno Libraries of the University of Nevada]
The Alfredian Boethius Project: Anglo-Saxon adaptations of the De Consolatione Philosophiae [a project at the University of Oxford]
Old English Graphotactics [maintained by Robert D. Stevick (University of Washington) and 'dedicated to editions of Old English texts that include the graphotactics of original manuscripts, and to studies of those texts'; at present Beowulf and Alexander's Letter are available.]
The Influence of Latin on Old English [a short essay by Edward Moore]
Awritan on Englisch: Englisch List Website -- A Forum for Composition in Old English ['an electronic discussion group dedicated to writing and communicating in Old English']
Computing with Accents, Symbols & Foreign Scripts: Old English ['This page covers utilities and codes for Old English characters...']