Are undead(excluding vampires) encountered in TES games sentient? I really wonder what the undead think, if they do. Whenever I see a zombie I think that it must have some form of conciousness. Do they, and if they do, whose conciousness is it? If they don't, then how can they see, hear, fight, and move independently with what appear to be senses or partial thought?

Well they're sentient, but they're not sapient. They're intelligent enough to know when to attack and when not to attack, but they don't actually think.

They don't have any thoughts or awareness at all? Are they nothing but puppets? What controls them and do they have souls?

I'm sure they have awareness. Like xXAntibodyXx said, they're sentient, not sapient.
(I have a feeling you've mixed up the two terms, so forgive me if you already know this, but sentience is being aware of your surroundings and reacting to stimuli- as in "OMG food!" [ie. zombies and skeletons], sapience means being able to think in abstract terms- like, "Elves taste very good. Especially their brains." [ie. liches and draugr])

No, I meant sentient in the sense that they feel pain and pleasure. It would be a nice bonus if you could tell me they had more complex awareness, but I'm wondering if they are even sentient at the lowest level. I have heard that they are just puppets without individual awareness. I also want to know if they have any thoughts as well, but I did mean sentient when I said sentient.

Well, pain and pleasure falls under "reacting to stimuli", so I'm guessing they do. They run away when Turn Undead or similar is used on them- if they weren't sentient, they wouldn't let it bother them and they'd keep attacking.

I doubt zombies have thoughts, think of them like unintelligent animals, they have basic instincts (most likely put in place by a necromancer), but cant think on a higher level, for example, they couldnt solve a puzzle.

Are they themselves sentient, or is it just some other force controlling the old bones and bodies? How do these dead bodies become living and aware again, even with necromancers? Do they have the souls of the original users of the bodies? Does soul trap work on the undead? Shouldn't they have some soul then? What are ghosts and wraiths then? Are they sapient? Are they sapient at all? What is it that controls these creatures? Even non-sapient animals have some individual awareness and sentience, so where do the undead get their awareness and sentience from?

You can trap their souls, so I'm guessing they're not just animated by magic. There's some kind of soul at work there, so logic dictates their awareness is their own.

I imagine necromancy works a lot like Daedra summoning (they use the same game mechanics after all). The summoned creature is yours to command, but if you're not powerful enough they'll break free and eat you. Sort of like a tiger in a magic act.

What of ghosts and wraiths? Are they sentient? What binds them to the mortal world? Also, how does a creature that isn't sapient wield a weapon. Skeletons use weapons, but does that not require some sapience?

I'd imagine the soul gives them some form of self preservation, as to their thought process it probably goes something like "Intruder. Kill." Zombies just obey what their necromancer has "programmed" them to do. Ghosts are quite a different matter, they appear to have varying levels of intelligence, there are the ones you commonly kill, that just moan and lounge about, and then theres ghosts that can actually speak to you, like the ones in the KOTN priory.

That seems right. However, are skeletons bound to any mission or area, or are they free? You were referring to skeletons in that first sentence, right? I imagine zombies are like mindless animals and their instinct is what guides them, or in some cases, a necromancer's order are their instincts. Skeletons seem a bit more intelligent though, just because they can wield weapons, especially a bow. Ghosts are basically body-less souls right? Are the ones that just groan and lunge about sapient? They are the souls of people, so how can they not be intelligent?

A created undead will work on the command of the necromancer or whomever created it. If it was a self-risen skelly, it's likely to have some intelligence, though most likely driven somewhat mad and aggressive, due to the effects of the Dreamsleeve. I'd pretty much say they fall into the rules of ghosts. Liches are an exception, in that they're completely aware, thinking, and working. Think of them as a person, only slightly decayed, ageless, and smelly.

Use my link to make some deductions. Note, souls are not required to rise an undead being.

I knew about liches already. How do skeletons rise by themselves?

Curses, Magic, Unfinished business that a ghost can't do.

Lots of milk.