This strategy, known as the method of loci, should also work for passwords, right?
You enter the forum romanum seeing Septimius Severus's triumph arch, turn to the right and pass the rostra to face the temple of Saturn. You password is... "Se2roS".
For your Yahoo! Mail password, you could also rely on password recovery, of course:
›› Not all is lost if your Yahoo! Mail password is lost.