Skyrim:Conjure

Conjure (a.k.a. Summon) causes the requested creature to appear and fight by your side.  A different magical effect is used for each different creature that can be conjured.

When you cast a Conjure spell, the creature will appear at the location where you are currently aiming.  If you are aiming at a point that is too far away from you, the crosshairs on your screen will turn red, indicating that it is impossible to cast the conjure spell in that direction; you will need to point towards a closer location before releasing the cast button.

Enchanting
The following items use this effect, but they cannot be disenchanted.
Aetherial Staff 
Sanguine Rose
Sild's Staff
Staff of Ancestors 
Staff of the Familiar
Staff of the Flame Atronach
Staff of the Forefathers 
Staff of the Frost Atronach
Staff of the Storm Atronach

Spells
The following spells use the Conjure group of effects. Following each spell is the specific variant of the effect that it uses:
Conjure Ancient Deathpriest : Conjure Ancient Deathpriest ( ;  )
If you have unlocked the Dark Souls perk, effect replaced with  
 : Conjure Ash Guardian ( ;  )
Conjure Ash Spawn : Conjure Ash Spawn ( ;  )
Conjure Ayleid Lich : Conjure Ayleid Lich ( ;  )
Conjure Bone Colossus : Conjure Bone Colossus ( ;  )
If you have unlocked the Dark Souls perk, effect replaced with  
Conjure Boneman : Conjure Boneman ( ;  )
Conjure Cursed Spectre : Conjure Cursed Spectre ( ;  )
If you have unlocked the Dark Souls perk, effect replaced with  
Conjure Dark Seducer Archer : Conjure Dark Seducer Archer ( ;  )
Conjure Dark Seducer Warrior : Conjure Dark Seducer Warrior ( ;  )
Conjure Dragon Priest: Conjure Dragon Priest ( ;  )
Conjure Dremora Lord: Conjure Dremora Lord ( ;  )
Conjure Familiar: Conjure Familiar ( ;  )
Conjure Flame Atronach: Conjure Flame Atronach ( ;  )
If you have unlocked the Elemental Potency perk, replaced by: Conjure Potent Flame Atronach ( ;  )
Conjure Foul Zombie : Conjure Foul Zombie ( ;  )
Conjure Frost Atronach: Conjure Frost Atronach ( ;  )
If you have unlocked Elemental Potency, replaced by: Conjure Potent Frost Atronach ( ;  )
Conjure Golden Saint Archer : Conjure Golden Saint Archer ( ;  )
Conjure Golden Saint Warrior : Conjure Golden Saint Warrior ( ;  )
Conjure Haunting Spirit : Conjure Haunting Spirit ( ;  )
If you have unlocked the Dark Souls perk, effect replaced with  
Conjure Malignant Zombie : Conjure Malignant Zombie ( ;  )
Conjure Mistman : Conjure Mistman ( ;  )
Conjure Putrid Zombie : Conjure Putrid Zombie ( ;  )
Conjure Seeker : Conjure Seeker ( ;  )
Conjure Skeleton Champion : Conjure Skeleton Champion ( ;  )
If you have unlocked the Dark Souls perk, effect replaced with  
Conjure Skeleton Marksman : Conjure Skeleton Marksman ( ;  )
If you have unlocked the Dark Souls perk, effect replaced with  
Conjure Skeleton Minion : Conjure Skeleton Minion ( ;  )
If you have unlocked the Dark Souls perk, effect replaced with  
Conjure Skeleton Warlock : Conjure Skeleton Warlock ( ;  )
If you have unlocked the Dark Souls perk, effect replaced with  
Conjure Staada : Conjure Staada ( ;  )
Conjure Storm Atronach: Conjure Storm Atronach ( ;  )
If you have unlocked Elemental Potency, replaced by: Potency: Conjure Storm Atronach ( ;  )
Conjure Tomb Guardian : Conjure Tomb Guardian ( ;  )
If you have unlocked the Dark Souls perk, effect replaced with  
Conjure Undying Ghost : Conjure Undying Ghost ( ;  )
If you have unlocked the Dark Souls perk, effect replaced with  
Conjure Wrathman : Conjure Wrathman ( ;  )
Conjure Zombie : Conjure Zombie ( ;  )
Flame Thrall: Conjure Flame Thrall ( ;  )
Flaming Familiar: Conjure Flaming Familiar ( ;  )
If you have unlocked Elemental Potency, replaced by: Conjure Potent Flame Thrall ( ;  )
Frost Thrall: Conjure Frost Thrall ( ;  )
If you have unlocked Elemental Potency, replaced by: Conjure Potent Frost Thrall ( ;  )
Pride of Hirstaang : Pride of Hirstaang ( ;  )
Storm Thrall: Conjure Storm Thrall ( ;  )
If you have unlocked Elemental Potency, replaced by: Potency: Conjure Storm Atronach ( ;  )
: Conjure  Sundered Shade ( ;  )
If you have unlocked the Dark Souls perk, effect replaced with  
Summon Arvak : Summon Arvak ( ;  )
Summon Daedric Horse : Summon Daedric Horse ( ;  )
Summon Gargoyle : Summon Gargoyle ( ;  )

Notes
Unless you have unlocked the Twin Souls perk, only one creature or NPC can be conjured or reanimated at a time. Conjuring a second will cause the first to vanish.  Twin Souls allows two conjured or reanimated at once.
The Necromantic Grimoire Creation adds equipment that increases this limit by one. It also adds conjure spells that conditionally bypass this limit.
On occasion, a summoned creature will remain in place for a long time after it should have vanished. It will remain near where it was summoned and attack people nearby (even the player if they return to the area), this is caused by the player changing cells or fast travelling before the summoned creature has properly spawned.

Bugs