Morrowind:Levitate

Causes the target to be able to walk on air.  The speed of movement through the air is determined by the value M, and also by the character's Speed attribute.  This can be used both to reach high inaccessible places and also to gain an advantage in combat.  Attacking non-flying, non-archer/mage opponents while levitating will often cause them to run away in terror since they are unable to hit you. Casting levitate on friendly targets does not start combat.

Levitation can also be used as an offensive spell if its strength is set to a low value. It costs little magicka and renders enemies almost immobile, similar to burden. 

You may not rest on the ground while levitating, but you can rest in a bed.  You may also find that in some cramped quarters, it will be impossible to move while levitating, as your head gets stuck in the ceiling.  You should also be careful to keep an eye on the duration of the spell so that it does not wear off while you are in mid-air, causing you to fall and get hurt or even killed.  (A Slowfall spell or any other method can help prevent this.)  There does not seem to be any known height ceiling to levitation.  You can keep going up for a very long time, long after the game-fog completely obscures your view of the ground. If you cast a Levitate spell, and then use fast travel, the spell will continue to its full duration as if the travel was instantaneous, even though in game-time it can take hours on certain routes.

Notes
Athletics plays no role on levitation speed. Levitation speed is purely a factor of Speed and Encumbrance.
Using Levitate 1pt with Fortify Speed is a lot more efficient than increasing the magnitude of Levitate. However as a spell it will be governed by either Alteration or Restoration depending on which is lower, and as an enchantment Levitate must be the first effect and its Fortify Speed needs to be at least 2 pts.
With a high enough intelligence it is possible to get an effective speed well above 100 by creating potions (if you have problems with moving too fast to control your character try switching to third person as this slows you significantly).
The speed of Levitate overrides the movement penalty from swimming. For characters who already have high speed boosts (such as from the Boots of Blinding Speed) or poor Athletics, a single point of Levitate can dramatically speed up a character's movement through water.
You cannot levitate in Mournhold. The in-universe reason given is that levitation offends the goddess Almalexia, but the technical reason is presumably because the city is in an interior cell, and levitation would make it possible to fly over the walls and see the unrendered world beyond.
Several items offer you the ability to levitate. You can find a guaranteed Steel Blade of Heaven in Odirniran, and you will be given the Travel-stained Pants over the course of the Main Quest. The Boots of the Apostle artifact also possess a levitation enchantment.

Related Effects
Jump, Slowfall, Fortify Acrobatics, Fortify Speed

Alchemy Ingredients
The following ingredients can be used to make a potion of Levitate:
Coda Flower
Racer Plumes
Sweetpulp 
Trama Root

Bugs
 
  This bug affects different races differently. For example, a levitating Altmer leaving the Redoran Underworks or entering the Balmora Mage's Guild from the main door is guaranteed to snag, while a Bosmer in both of those situations will not snag.