No, with one exception.
Touch spells are not weapons, though they may be treated as weapons for certain effects, such as the Touch Range section of the SRD, which says (emphasis mine):
A touch spell that deals damage can score a critical hit just as a weapon can. A touch spell threatens a critical hit on a natural roll of 20 and deals double damage on a successful critical hit.
or the Weaponlike Spells section of Complete Arcane (p72) which says (emphasis mine):
Any spell that requires an attack roll and deals damage functions as a weapon in certain respects.
This is pertinent since the Nonlethal Damage section of the SRD says (emphasis mine):
You can use a melee weapon that deals lethal damage to deal nonlethal damage instead, but you take a –4 penalty on your attack roll.
Thus touch spells are not weapons, but can act like them in certain, defined, circumstances. Being able to deal nonlethal damage at will for an attack penalty is not one of them.
However, if a spell produces a melee weapon that you can attack with, even as touch attacks, then you can attempt non-lethal attacks with the produced weapon.