I think the most comprehensive teaching site for learning material is Barbara Ann Fackler’s well constructed web site. Barbara is a brilliant harpist and scholar with great ideas.
Probably the most comprehensive site for purchasing harp print music and PDF downloads is Melody’s Traditional Music. Melody’s has a large selection of music for the diverse student and performer, from beginners to advanced, both lever and pedal harp.
Harp Strings – for lots of information on harp strings:
Below is a video you might enjoy. It is a tune learned in the Irish Aural Tradition back in 1996 at the Milwaukee Irish Fest. I am able to teach that style, as well as traditional note reading.