http://leagueoflegends.wikia.com/wiki/Cleanse
Cleanse will remove any and all of the following effects: blind, charm, flee, slow, polymorph, silence, root (sometimes called Entangle, Snare or Immobilize), stun and taunt.
http://leagueoflegends.wikia.com/wiki/Quicksilver_Sash
All forms of crowd control
Will remove almost all DoT damage from abilities, including but not limited to: Blaze, Noxious Blast, Grog Soaked Blade, Malefic Visions, Poison Trail, Toxic Shot, and Deadly Venom.
Shows what Cleanse does and doesn't remove. QSS removes just about every debuff other than knockups.
