"Luminarium: John Donne"
http://www.luminarium.org/sevenlit/donne/
This "online anthology" draws on information from Norton, the Cambridge guides, and other literature standards and collects it freely. Information is sourced to provide students with starting points for their own research. Students can explore Donne's whole oeuvre here, as well as the work of Donne's contemporaries, influences, and successors.
"Digital Donne: A Complete Concordance"
http://donnevariorum.tamu.edu/resources/completeconc/
Students can use concordances as a resource to trace particular language use, themes, and characters across Donne's poems and sermons.