Is an Ooze or something with Ooze traits a living creature for the purposes of things like Vampiric Touch?
If we look at the entry in the SRD we see:
An ooze is an amorphous or mutable creature, usually mindless.
So it is, unequivocally, a creature.
As for living, the entry doesn't say that they aren't, unlike construct:
Since it was never alive, a construct cannot be raised or resurrected.
Undead are once-living creatures
And an Ooze does fulfill the major requirements of most definitions of life:
Oozes eat and breathe
(I'll assume they reproduce, it just doesn't often come up in game except for the varieties that split when you deal them enough damage)
If we look up the Ooze ( http://www.d20srd.org/srd/monsters/ooze.htm ) itself, we find that: "Oozes are amorphous creatures that live only to eat." So the answer, if we take even description as word for word canon, is most likely "yes". :)
Check the creature's Type in the glossary of the Monster Manual. Undead and constructs share the following trait:
- Not subject to critical hits, nonlethal damage, ability damage, ability drain, fatigue, exhaustion, or energy drain.
If the creature's type does not have this trait, then the creature can be affected. The MM glossary entry for the Ooze type (p. 312-313) shows that they do not have this trait. They are, however, immune to certain other affects: poison, sleep, paralysis, polymorph, stunning, and mind-affecting effects (and blinding, since they have blindsight).
I would classify Vampiric Touch as an energy drain, for this purpose, though the spell description isn't that specific.