Banwarth's Irish Guitar and Bouzouki: Guitar and Bouzouki in Irish traditional music. TablEdit tabs, scores, MIDI, and tips.
DADGAD: A collection of tunes in midi and tablature (pdf format) for guitars in DADGAD tuning. Also includes advice on playing technique.
Doc's Workshop: A collection of Celtic tunes arranged for guitar (especially that of Turlough O'Carolan) in a variety of formats.
Irish DADGAD Backup Guitar Resources: Advice on playing Irish traditional music in a DADGAD tuning; includes chord shapes (in PDF format).