I pronounce them all the same way (HAY-lee). Hailey feels the most natural to me, followed by Haley. I don't care for Hayley, it looks too trendy with two Y's.
Let us step into the night and pursue that flighty temptress, adventure.
PNL: http://www.behindthename.com/pnl/45898
Top: Alice and Elias
Bottom: Kensi and Alve