My Duskblade channels shocking grasp,and misses with his attack. Next round he full action attacks and misses with his first attack. For his second attack could he take his hand off his two handed weapon and make a touch attack with his shocking grasp? As per the players guide on holding the charge you do not loose the spell until you hit with it or cast another spell. I previously asked if you channeled shocking grasp if you could change the energy type by using gauntlets of energy transformation and was told the shocking grasp isn't in the weapon it channels when you make the hit. So if you cannel the spell in round 1 and miss you are still holding the spell in round 2. Holding the spell from round 1 you use the full attack action in round 2, miss with your weapon attack in round 2. As your second attack in round 2 can you take your hand off your two handed weapon as a free action and make a touch attack as your second attack?
The assumption that the spell is "in your hand", especially the particular hand you cast it on originally is not following RAW. As written, there is no specification and you can muck around with weapons etc until you discharge the spell. The discharge rules do not prevent this.
So in this scenario you can simply choose that the Duskblade tries to hit with his second attack using either his weapon or as an unarmed strike or an unarmed touch attack.
In my view, the confusion comes from mistaking a hit roll and damage roll as representing a single strike with a single weapon when it is really an abstraction of 6 seconds combat using the weapons to hand. Thus there are not rules for a pommel strike when it can easily be represented by a low a roll with your damage dice.
You can't cast a spell to replace a weapon attack in a Full Attack, because spells aren't weapons. Because:
A Full Attack takes a Full Round Action, and is resolved by making weapon attacks following your BAB.
Casting Shocking Grasp is a Standard Action, and is resolved by making a melee touch attack.
Quite simply, a spell does not count as a weapon, and you use your weapons to resolve a Full Attack.
However, being a duskblade, you can channel the spell simply by hitting the enemy with your sword, which can be done during your Full Attack. However, the damage is only applied on one attack.
Also, I see no reason why you would release your weapon to apply it with your hand, instead of simply channeling it. While the weapon damage is only applied when you beat a creatures total AC, the spell damage is applied once you beat it's touch AC, just like if you were casting the spell normally.