Reduced Movement Speed

There are many Skills and Abilities in Diablo 3 that you can use to slow down, reduce/decrease the movement speed of your enemies. Slowing down the movement speed of enemies can be extremely helpful, whether you are trying to finish off a foe or simply flee from the battle. Slow effects are particularly effective when used on enemies that rely on speed, such as Fetishes.

Also See:
Chill

The Following Is A List Of Each Class' Skills That Can Slow Enemy Movement:

Barbarian Skills That Decrease Movement Speed

Hammer of the Ancients (The Devil's Anvil)
Threatening Shout (Initimidate)
Cleave (Gathering Storm)
Leap
Weapon Throw
Ground Stomp (Deafening Crash)
Earthquake (Chilling Earth)
Ancient Spear

Demon Hunter Skills That Decrease Movement Speed

Caltrops
Rapid Fire (Web Shot)
Entangling Shot
Elemental Arrow (Frost Arrow)
Fan of Knives
Companion (Spider Companion)

Monk Skills That Decrease Movement Speed

Lashing Tail Kick (Sweeping Armada Kick)
Lashing Tail Kick (Hand of Ytar)
Dashing Strike (Soaring Skull)
Crippling Wave
Exploding Palm (Creeping Demise)
Inner Sanctuary (Sanctified Ground)
Tempest Rush
Mantra of Conviction (Dishearten)
Mystic Ally (Water Ally)

Witch Doctor Skills That Decrease Movement Speed

Poison Dart (Numbing Dart)
Grasp of the Dead
Haunt (Grasping Spirit)
Corpse Spiders (Medusa Spiders)
Soul Harvest (Languish)
Sacrifice (Black Blood)
Wall of Zombies (Unrelenting Grip)

Wizard Skills That Decrease Movement Speed

Ice Armor
Wave of Force
Spectral Blade (Impactful Blades)
Slow Time
Ray of Frost
Arcane Torrent (Arcane Mines)
Blizzard (Grasping Chill)
Meteor (Comet)
Temporal Flux (Passive Skill)- Whenever you deal Arcane damage, enemies are slowed by X% for X seconds.

Follower Skills That Decrease Movement Speed

Templar (Intimidate)
Scoundrel (Crippling Shot)
Enchantress (Powered Armor)
Enchantress (Scorched Earth)