There are 24 Sorceries in the game. I will first list them in the order they appear in your inventory, then I'll explain how they can be obtained.
*** Spoiler - click to reveal ***Soul Arrow
Great Soul Arrow
Heavy Soul Arrow
Great Heavy Soul Arrow
Homing Soulmass
Homing Crystal Soulmass
Soul Spear
Crystal Soul Spear
White Dragon Breath
Magic Weapon
Great Magic Weapon
Crystal Magic Weapon
Magic Shield
Strong Magic Shield
Aural Decoy
Hush
Fall Control
Hidden Weapon
Hidden Body
Repair
Cast Light
Chameleon
Remedy
Resist Curse
Note that Dark Bead, Dark Fog, and Dark Orb found in Oolacile Township and the Chasm of the Abyss are not required as they are from areas that were part of the original game's DLC .
19 can be purchased from NPCSAural Decoy: sold by Griggs for 1000 souls
Fall Control: sold by Griggs for 1500 souls
Soul Arrow: sold by Big Hat Logan for 1000 souls
Heavy Soul Arrow: sold by Big Hat Logan for 2000 souls
Magic Weapon: sold by Big Hat Logan for 3000 souls
Magic Shield: sold by Big Hat Logan for 3000 souls
Great Soul Arrow: sold by Big Hat Logan for 6000 souls
Great Heavy Soul Arrow: sold by Big Hat Logan for 8000 souls
Homing Soulmass: sold by Big Hat Logan for 20000 souls
Crystal Magic Weapon: sold by Big Hat Logan for 20000 souls
Homing Crystal Soulmass: sold by Big Hat Logan for 30000 souls
Soul Spear: sold by Big Hat Logan for 40000 souls
Crystal Soul Spear: sold by Big Hat Logan for 50000 souls
All of these spells are offered by Big Hat Logan once he is freed from the prison cell in the Duke's Archives and relocates to the small room near the Duke's Archives bonfire. Note that some of these spells are sold by Griggs and Rickert but you have to buy all of the spells that Logan sells to advance his questline, even if you have already bough them from someone else.
Cast Light: sold by Dusk of Oolacile for 1000 souls
Hidden Weapon: sold by Dusk of Oolacile for 2000 souls
Hidden Body: sold by Dusk of Oolacile for 2000 souls
Chameleon: sold by Dusk of Oolacile for 3000 souls
Repair: sold by Dusk of Oolacile for 10000 souls
Resist Curse: sold by Ingward for 5000 souls
Four are found on a corpse or in a chestRemedy: found in a chest in Blighttown across a precarious tree branch path near the top of the big wheel lift system
Hush: found on a corpse in Sen's Fortress near the interior area with rolling boulders
Strong Magic Shield: found in a chest in the Duke's Archives near a respawning Channeler enemy
Great Magic Weapon: found on the chandelier in Anor Londo which must be cut down from the rafters above
One is from an NPC questlineWhite Dragon Breath: dropped by Big Hat Logan after he goes crazy in the Duke's Archives and relocates to the room where you originally were killed by Seath.
NPC information Griggs of Vinheim relocates to Firelink Shrine after being freed from a locked building in the Lower Undead Berg. He will not offer to sell spells to you unless you have at least 10 Int.
Big Hat Logan relocates to Firelink Shrine after being freed from a cage in Sen's Fortress. He will not sell spells to you unless you have at least 14 (maybe 15) Int, but this requirement does not apply once he relocates to the Duke's Archives (which happens automatically once you get there yourself). He is first found in the prison section and will advance to a small room near the Duke's Archives bonfire once freed from his cell. You must buy all of his spells once he relocates to this small room, defeat Seath, then talk to him again so that he will relocate a final time to the room where you first encountered Seath.
Dusk of Oolacile is summonable near the edge of the lake in the Darkroot Basin near where the giant hydra is located. In order for her summon sign to appear, you must kill the hydra, then move across the lake and into a cavern area to defeat a golden crystal golem, freeing Dusk. Talk to her and answer "yes" when asked, at which point you can go back and summon her via her summon sign.
Note: Dusk’s summon sign disappears once you acquire the Broken Pendant from the Crystal Golem in the Duke’s Archives. After this point, you can buy her spells from Elizabeth, who is accessible after defeating the Sanctuary Garden in the Oolacile Garden.
Ingward is located atop a building full of ghosts in the New Londo ruins.
As always, refer to
http://darksouls.wikidot.com/ for specific information relating to items or locations.
This page gives specific information for each pyromancy.