According to Herodotus (4.13), they live beyond the Arimaspians and were visited by Aristeas. He also mentions a Homeric poem (now lost) which deals with them.
Large quantities of gold were here, guarded by the griffins.
Abaris, Ilithyia are Hyperboreans.
See also Thule (myth).
The cycle of Conan the Barbarian by Robert E. Howard is supposed to happen in the similarly named "Hyborian era".