Okay, correct formula and example.

Damage = [{(weapon base Damage + 1) * (1 + %EDmod from weapon/100 )} + (weapon base damage * socket %ED/100 ) + min/max damage from all equipment] x [Y / 100 + %ED from equipment other than weapon/100 + %ED from skills/100 + 1]

Easier written down:
Damage = [A + B + C] x [Y / 100 + D + E + 1]
A=(weapon base Damage + 1) * (1 + %EDmod from weapon/100 )
B=(weapon base damage * socket %ED/100 )
C=min/max damage from all equipment
D=%ED from equipment other than weapon/100
E=%ED from skills/100
Y=strength and dexterity bonus, see just below
The "Y" refers to your attributes:
- For bows and crossbows, use your dexterity value.
- For "hammer" weapons, use (1.1 x strength).
- For all thrown weapons (even in melee), use (0.75 x Strength + 0.75 x Dexterity)
- For class-specific spears, use (0.8 x Strength + 0.3 x Dexterity)
- For daggers (and Assassin claws), use (0.75 x Strength + 0.75 x Dexterity)
- For all other melee weapons, use your Strength value.

Example and explanation

200% Lightsabre with Ohm Rune, 200 strength, 350% ED from skills, none from other gear.
Hmm.. to explain it in full. You take the weapon base damage. That is, the damage a white item would do of the same weapon type. Lightsabre is a phase blade.
Phase Blade Base Damage: 31-35 (look this up on Diabloii.net or the Arreat Summit)
Now.. for %ED mods encased by magical properties, you have the weird occurrence that the weapon base damage is considered +1... The ED mod is calculated on 32-36 instead of 31-35.
So this means that:
A=((31-35) + 1)*(1 + 200/100)=(32-36)*(1+2)=(32-36)*3 = 96-108
Now for Ohm and %ED jewels socketed in a weapon, it gives a bonus on the normal base damage, so on 31-35.
B=(31-35)*(50/100)=(31-35)*0.5 = 15.5-17.5
(note that this only adds 33 damage, so maybe ohm wouldn't be a wise socket... it's expensive as hell, so socket it with a 30 max damage jewel instead for a very comparable result and its much cheaper to get and easier to craft. this max damage jewel should of course be taken into account when calculating the value for C)
If you didn't socket your weapon with an ED jewel or if it is already socketed, just take the damage the way it shows on your item and skip calculations A and B. Take that value as the result of A+B.
Lightsabre has a 10-30 damage mod. This means it adds 10 minimum and 30 maximum damage. For the example no other source of min/max is listed so:
C=10-30
We now have betwen the first []: (96-108) + (15.5-17.5) + (10-30) = (121.5-155.5)
I noted that we have a strength of 200. Swords don't get bonuses fromdex or anything, so this means our Y value is:
Y=200
I noted no other socketing of %ED or any other %ED modifiers from gear (here is the point to insert 350%ED to Demons (note, Demons only) from Laying of Hands, but not in this example)
D = 0
%ED from skills is purely 350%, don't ask me how and what skills, it's just an example.
E=350/100=3.5
This means on our second [] we have gotten: [200/100 + 0 + 3.5 + 1]=[2+0+3.5+1] = 6.5
Our final physical damage will then be (121.5-155.5) * 6.5 = 789.75-1010.75

I hope this "walkthrough" helps you calculate your damage.
[Chaos] : ^^, i hope that too -__-