(information provided by Anthony Esposito)
The new edition of the Oxford English Dictionary (currently being published online in quarterly instalments) is the first full-scale revision for 100 years. Lists of historical forms are being thoroughly revised and greatly expanded. To enhance electronic searching each individual form is being tagged with all of its attributes (i.e. date, provenance label, grammatical label, register label, as appropriate).
For further information about OED Online see the website (http://www.oed.com/)