What was the maximum password length for pre-sale wallets/accounts? While we're here, is there a maximum password length for accounts created now, using standard tools like geth/mist?
There are no limitations in the algorithms used.
Pre-sale wallets use PBKDF2 to derive a seed from the password. The current wallets use scrypt (which uses PBKDF2 internally) or PBKDF2 for the same. And that ultimately uses hashing on the passwords (in the case the password is shorter than the key length, it may not)
I don't think pyethsale placed a limitation on password lengths and probably none of the current software is.
It is always advised to load the wallet in another client after creating it in order to double check that it works.