Regular combat calculations are now split up into Dodge, Block and Parry on the defender's side. Dodge rolls are dependent on General Combat training. Parry is dependent on your weapon skill with the wielded weapon. Block is dependent on shield use skill. All three can be reduced by various situations (extreme fatigue, hunger, sitting or laying prone, being frozen or rooted in place, and so on).
If you wield two weapons you have two parry rolls; if you are holding two shields (weirdo) you get two block rolls. In either case the second roll has a small penalty. Holding a melee weapon and shield grants you one parry and one block with no penalties.
Ranged attacks cannot be parried. This includes arrows, shots and magical bolts (fireballs, etc.).
Certain weapons may grant bonuses or penalties to parrying or dodging. This information can be seen when EXAMINEing an item:
General weapon parry ratings by group:examine spear
The spear is mainly made of copper.
It could be wielded in melee combat, its effectiveness dependent on your Polearms skill.
The weapon feels of average balance, and you figure you could get up to 3 strikes per attack with it.
It could be wielded with either one or two hands.
It would allow you to keep a fair distance from opponents and dodge melee attacks more easily.
The weapon would give you a slight advantage at parrying incoming blows.
After hefting the spear a few times, you figure it weighs 5 pounds.
Roundtime: 5 seconds.
Staff = Best
Sword = Good
Polearm = average/good
Hafted = Below average
Dagger = Difficult (except the main gauche, which is good)
Chained/Bow = Terrible
Whip/Brawl/Firearm = Impossible
Rapier = Special (still working on it - you shouldn't be parrying a greataxe with a rapier)
Polearms all give dodge bonuses (some better than others), and a few of the larger hafted weapons and swords give a slight bonus. This is to simulate having a greater reach and therefore being able to keep further away from one's opponent. There are currently no dodge penalties to smaller weapons. At the moment I'm content with assuming the short reach penalties would be balanced out by "crowd press" tactics when used against opponents with larger weapons.