There's two more places I can think of.
In order of progression: Painted World of Ariamis
This is the place where I did my farming after Dark Root Garden wasn't cutting it anymore.
First, you will need to: Find the Peculiar Doll in the Undead Asylum on your second visit.
For instructions on how to return to Undead Asylum, check this video.
The doll can be found in the same cell where you started the game.
Reach Anor Londo and locate the big room where the Painted Guards are.
You will find a huge painting on the wall.
Descend to the floor level and touch the painting to be transported into the Painted World of Ariamis.
Progress through the level until you reach a sort of town square, where you will find a slew of Phalanx mobs.
These are the creatures you will be farming.
Across this courtyard, you will find a door that opens up and leads you to the starting bonfire.
You will need an AOE damage spell for this method.
Poison Mist is a good choice for low levels, since Phalanx are weak to poison.
They move slowly, so you can run up to them and cast Poison Mist one or two times while moving in circles around them.
Just wait for a few seconds and they will die.
With the Covetous Silver Serpent Ring equipped, this method will net you around 9000 souls in a few seconds.
Just run back to the bonfire and repeat.
If you are a caster class, you will be able to speed up the farming by using strong AOE spells.
For instance, I play a faith build character.
My Wrath of the Gods spell managed to kill all Phalanx with a single cast, netting me 9000 souls every 20 - 30 seconds.
I spent more time running up to the town square than killing them.
The Homeward miracle will speed up this process considerably.
Now this method requires you to side track from the main story progress.
Another method you can try, which doesn't require you to do any side-quest is farming Dark Anor Londo.
Dark Anor Londo:
After beating the Ornstein and Smough encounter, you will meet Gwyneavere.
If you hurt her she will disappear and Anor Londo will become Dark.
Warning:
Making Gwyneavere disappear means you won't be able to join the Princess' Guard covenant for the rest of your current play-through.
In Dark Anor Londo, only Painted Guards and Silver Knights will remain, the rest will be gone, including the giants and archer right outside Ornstein and Smough's fog wall.
Instead, you will find two NPCs here.
You can kill them for around 6000 souls with the Covetous Silver Serpent ring equipped.
The trick is, they will only respawn if you leave Anor Londo and return.
However, you can use Homeward Miracle to return to the previous bonfire where you rested at.
The NPCs will also reappear.
gaming.stackexchange.com/users/13109/Pedro Mancheno
The painted world I leveled up to level 123 there in my opinion its the best place to grind use the symbol of avarice (rare drop from mimics) and the gold serpent ring and 15 humanity and your soul rate
should skyrocket
I did it for a very short time also.
gaming.stackexchange.com/users/66808/justin
In my opinion the best place to farm souls at later soul levels is the Tomb of Giants.
Right at the end of the tombs before the Gravelord Nito bossfight, there is an area with infinitely directly respawning baby skeletons.
While they only grant 100 Souls each on new game, they are killed in one hit with a decent weapon, and you will most likely kill several of them with one strike.
And they respawn within seconds, which means you won't have to go back to the bonfire.
Additionally, they drop humanity fairly commonly (especially with the Gold Serpent ring and some humanity), so it is a good place to farm both at the same time.
You can get thousands of souls and quite a bit of humanity very fast there.
gaming.stackexchange.com/users/54958/Kodama
Being that glitches are accepted answers , the dupe glitch can be used on any boss soul to use the soul without being consumed.
This can actually be used on any consumable with a confirmation prompt, including Fire Keeper Souls which give you +5 humanity when consumed and a full heal.
gaming.stackexchange.com/users/45820/Mondrianaire
Well I farm at Anor Londo before disrupting the princess, after killing Ornstein and Smough.
Rest at the princess bonfire.
Just killing the 2 sentinels and the knight will give you just under 10000 souls (with gold covenant ring and mimic hat) and only takes 1 min.
And if you kill the 2 minor sentinels and the 9 lighting bros, that gives you over 10000 more.
With my claymore at +15, it takes me about 1 1/2 mins.
gaming.stackexchange.com/users/176286/Kyle
I'm already aware of:   The sealed area of Darkroot Garden.   This is normally a fantastic area to grind, but I'm currently in theForest Hunter covenant and need to stay in it so I can purchase itemsfrom Shiva of the East.   In the Undead Burg, shooting the dragon causing him to kill theundead soldiers on the bridge.   This is fine for lower levels, but at SL50, 300 souls per go doesn'treally cut it anymore.  Are there any other good areas for soul farming?
What areas offer serious soul farming?
gaming.stackexchange.com
<dark-souls>
gaming.stackexchange.com/questions/42966
gaming.stackexchange.com/users/1613/YellowMegaMan
At later soul level, the bext place is the Tomb of Giants? You can also farm at the Painted World or Ariamis and Anor Londo. Players propose a series of areas to fulfill the task of farming souls.
Listed areas to farm souls, based on player experiences.