benzonic acid and phenol, which one is more acidic and why?

In view of the resonance structures of benzoate and phenoxide ions:
Benzoate ion

圖片參考：http://i117.photobucket.com/albums/o61/billy_hywung/Aug08/Crazyorg5.jpg

Phenoxide ion

圖片參考：http://i117.photobucket.com/albums/o61/billy_hywung/Aug08/Crazyorg6.jpg

Mainly there are two reasons:

Benzoate ion has more resonance structure.
For phenoxide ion, the last 3 structures in the diagram have their "-" charge on the nuclear C atoms (on the benzene ring), meaning that they are of higher energy profile (since C is less electronegative than O) which have less contribution to overall hybrid. Thus it is less stable.
So overall speaking, benzoate ion is more stable than phenoxide ion and hence benzoic aid is more acidic.