I usually choose bcrypt when hashing as I can set the work factor to slow down the calculations of the hash. However, I have to keep a copy of the hash in order to verify it (since it includes the salt) when the same input comes around again.
Are their any A) common and B) slow hashing algorithms that do not require a salt? In other words, I don't need to preserve the output state in order to calculate the exact same hash again?
I am not looking for a more secure/unbreakable hash - just one that takes a long, long time to work out.
At this point it seems that multiple rounds of SHA-256 is my current best option.