If you think about it, you'd be channeling it through an object, which may or may not be a weapon. This type of feat would allow you to do a touch attack through say, a bartop. Or through a wall. Or through floorboards.

That's really high powered.

There's also a prestige class that allows this but I don't remember which one.

There's the Spellsword prestige class, which lets you channel any spell through your weapon, not just touch spells.

I thought there was a feat to do it, but I can't seem to find it in any of my books.

What do you hope to accomplish? Cast spell, then next round swing your weapon to do d8+3d6 with your longsword + shocking grasp damage?

Or are you looking for a way to deliver the touch spell at range?

If it's the former, you'll only be able to pull it off every other round, and I'm not sure it's really worth it.

If it's the latter, the Reach Spell metamagic feat will cover your needs. Any touch spell becomes target within 30'.

I was thinking of the former. I guess I hadn't thought through that I might need to use two different rounds, since usually Shocking Grasp can be discharged in the same round as it's cast. I think it probably still would be worth it, since my weapon is vampiric.

I will look into Reach Spell though, thanks!

In that case, the spellsword's 4th level ability is probably what you're looking for (it's in Complete Warrior).

The Duskblade (Players Handbook 2) gets an ability called Arcane channeling at level 3 that allows the character to channel spells through weapons as a melee attack.

Does this mean the spell effect replaces the weapon damage or in addition to the weapon's damage.

IIRC, when the attack succeeds the weapon deals damage, and then the spell effect resolves.

Or Spectral Hand, so you don't have to blow a feat.

Actually, I know that I read about one somewhere this past weekend, but I do not have my books handy to look it up. There is a Feat that I was considering that does exactly this, as I was looking at it for my cleric to possibly channel Cure spells through his mace. I will look for it tomorrow and see what I can come up with, but it was most likely in Complete Divine or Book of Exalted Deeds.

You can also try asking at the Wizards of the Coast official website. The guys on their forums are incredibly helpful.

I think there is a feat in the Players handbook 2 which is called Smiting Spell I think.

You could also get the spellstoring enhancement on your weapon(a +1 bonus I believe), though that might take longer than you want since you have to cast it into the weapon, then attack. But you don't use up a feat slot

In one of the Dragon Mags from earlier this year, there was a thing whereby a Wizard took a staff in lieu of a familiar, and got all kinds of funky abilities with said staff. That was one of them.

Like Item Familiars ?

Not really, no.