I have always been fond of Donkeyskin - the folk/fairy-tale version with the dresses and the trunk that travels underground. Largely because of the dresses, and because the princess has gumption.

Tam-Lin, in a myriad of tellings - Fire and Hemlock by Diana Wynne Jones, Winter Rose by Patricia McKillip, the ballad, etc.

Then there is Ursula K LeGuin's The Tombs of Atuan, which certainly had a formative influence on me, and for sheer word-wonder, just about everything Patricia Mckillip has written, particularly Ombria in Shadow and Song for the Basilisk.