You can start with this patch to encfs: http://code.google.com/p/encfs/issues/detail?id=110 i hope it will be merged.

then you can check password even without mounting the drive, so it will be possible to use encfs for login.

Main reason for this is that /etc/shadow may be possibly cracked faster than encfs which is problem if you are using single-password model (same password for encfs and login).

You should also make it possible to change encfs password using pam_encfs (it's not so hard to add such functionality to pam moduel).