For much more detailed NPC damage/armor, check out

http://eve.grismar.net/rats/index.php
http://www.npc.elfarto.com/index.php

**NPC\xb4s Damage**
Angel's = Explosive/Kinetic
Minmatar = Explosive/Kinetic
Thukker Tribe = Explosive/Kinetic
Blood Raider = Thermal/EM
Ammatar = EM/Thermal
Ammar navy = EM/Thermal
Sansha's = EM/Thermal
Mordu's legion = EM/Thermal/Kinetic
Mercenary Commander = EM/Thermal
Khanid Kingdom = EM/Thermal
Mercenaries = Kinetic/Thermal
Guristas = Kinetic/Thermal
Serpentis = Thermal/Kinetic
Rogue Drones = Thermal/Kinetic/EM

**Damage types to use Against Enemy***
Angel - EM(shields)/Exp(Armor) & Thermal
Amarr Navy - EM(shield)/Exp(Armor)
Mordus - EM(shield)/Exp(Armor)
Gurista - EM(shields)/Exp(Armor)/Therm & Kinetic
Blood - Therm
Sansha - Therm
Serpentis - Therm
Mercenary - Exp
Caldary Navy - Exp/Kin/Therm
Khanid - EM(shields)/Exp(Armor)
Zazzmatazz - EM(shield)/E