About Middle English Grammar [a PDF file by Scott Kleinman (California State University, Northridge)]
The Middle English Scribal Texts Programme (MEST) [a project ongoing at the University of Stavanger]
englesaxe: Early Middle English for today [a fairly comprehensive and approachable guide to the language, literature and society during the Early Middle English period]
A Companion to ME Literature [pedagogically oriented text synopses and commentaries, developed at the Heinrich-Heine-University Duesseldorf]
Harvard's Geoffrey Chaucer Website ['How to Read Chaucer' and 'Middle English Teaching Resources Online' are particularly relevant to HEL. The pages in the previous version of the website which are particularly relevant to HEL are 'Teach Yourself to Read Chaucer's Middle English', 'Chaucer's Pronunciation, Grammar and Vocabulary' and 'The English Language in the Fourteenth Century: The Status of English'.]
Chaucer MetaPage [list of links to Chaucerian resources]
Open Access Companion to the Canterbury Tales ['a volume of introductory chapters for first-time, university-level readers of Geoffrey Chaucer’s The Canterbury Tales']
Peter Robinson (University of Saskatchewan), CantApp [includes a 45-minute narration of the General Prologue and a line-by-line translation; see the press release here, here and here.]