http://npc.elfarto.com/index.php
Its ingame browser compatible. Just type in the name of the NPC and look.
When deciding which type of damage to deal and if you use projectiles, missiles, or drones, sum the shield and armor resistances. The smallest sum should be the damage type to use. If you're using hybrids or lasers, then you're kinda stuck. Lasers vs. Angels is a lesson in pain.
For projectiles:
Kinetic: Titanium Sabot
Explosive: Fusion
Thermal: Phased Plasma
EM: EMP
When deciding to harden, check the DPS line. Usually the forumala goes. Coincidentally, the damage types that NPCs deal are usually the ones they're weakest against:
Blood/Sanshas/Amarr/Khanid/Ammatar: EM/Therm.
Serpentis/Guristas/Caldari Navy/Gallente Navy: Kin/Therm. Therm/Kin for Gal/Serp
Angels/Minnie: All damage types, with a slight focus on Exp/Kin. Its easier to tank using just 3x Invuln IIs for shield tanking (or 2x Invuln and an EM) and a bunch of Energized Adaptives and an Explosive Hardener for armor. Shield is slightly easier since Exp damage has a naturally high shield resist. I get around 85% or so with 3 Invuln IIs and a named damage control.