Aer Lingus has just announced a twice-weekly service from March 2007 between Dublin and Santiago, prices starting at €19 one way + taxes.
http://www.flyaerlingus.com/
Update 21.12: Tuesdays and Saturdays from March 27
http://www.flyaerlingus.com/
Update 21.12: Tuesdays and Saturdays from March 27