You could do almost anything on the harp. Pick music you like, I think of the slow melodic Scottish and Irish songs and play it on the harp. You don't need special harp music - regular music notation should be fine. There are some harp books - I'll look on my shelf in a minute- but any music would work.

Are you aware of the various harp societies? The International Society of Folk Harpers and Craftsmen produces the Folk Harp Journal [ISFHC; 4718 Maychele Drive; Anaheim CA 92807-3040], Scottish Folk Harp Society produces The Kilt and Harp journal [Sandra Sparks; 1243 Druid Place #1; Atlanta GA 30307], The Welsh Harp Society produces Y Delyn [Karen Mueller; 838 Elgin Ave; Forest Park IL 60130]. All of these addresses are several years old.

some books:
Alison Kinnaird The Harp Key
Deborah Friou Renaissance Music
Sylvia Woods 40 O'Carolan Tunes
Taigh Na Teud Traditional Tunes for the Clarsach
but any book of Scottish, Welsh, or Irish songs should work.