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For party buffs the following are good options for a cleric:
1. Prayer: Bonuses on damage and attack.
2. Blessing of Fervor: Cleric haste spell with more options.
3. Bless
4. All the stat buff spells you can obtain.
5. Resist Energy
6. Death Ward
7. Spell Resistance
8. Spell Immunity
9. Protection from Evil or the protection line of spells or Magic Circle
10. Invisibility Purge: Better than see invisibility and the like because it is not stopped by Mind Blank or Nondetection if you run the spell blocking see invisibility.
11. Wrathful Mantle: New in APG. Save bonus and allows warded creature to do some damage.
Oracles due to limited spells are harder to spec for buffing rather than healing, especially if you are the only healer. But if you do your research, you can make an effective buffing oracle. Clerics are pretty good at providing defensive buffs. Not as good at offensive buffing as a mage, but still not too far behind. Takes more research to figure out good selections for offensive buffing.
Hopefully the above list gives you a place to start.