RaiderSec has an older article on how major browsers store passwords.
Before anyone pontificates about how terrible of a job these browsers did, I’d like to point out the impossibility of encrypting something when all encryption keys are on disk. Firefox allows you to set a master password, at which point your passwords are stored fairly securely.
Alternately, I use LastPass and highly recommend it. The UI is weird, but once you get used to it, it is quite powerful.