Can a duskblade use his Arcane Channeling ability to channel the spell magic weapon? I haven't found this dealt with anywhere.
Arcane Channeling can channel any spell that has a range of touch.
The first weapon you touch during your attack action on the round which you channel Magic Weapon gains an enhancement bonus to that weapon. If you resolve Arcane Channeling with Shocking Grasp, you deliver that spell upon hitting the target specified in the spell.
The target of Magic weapon is a weapon touched, the target of Shocking grasp is a creature touched.