As far as blogging software goes, it's hard to go wrong with Movable Type. It is open source, supports PostgreSQL (unfortunately, due to be dropped in MT5.0, hopefully it will be re-added in 5.1), supports multiple users and blogs out of the box, can operate in static, partial-dynamic, and full dynamic mode.
If for some reason you or a user forgets their password you can reset the password via the following SQL commands
PostgreSQL
Make sure to install the postgresql-contrib package if you don't already have it installed.
Install the crypto functions into the Movable Type database, this is a one time task.
psql -d movabletype -f /usr/share/pgsql/contrib/pgcrypto.sql
Now connect to the movabletype database and run the following command to reset a password:
UPDATE mt_author SET author_password = crypt('the-new-password', gen_salt('des')) WHERE author_name = 'USERNAME-GOES-HERE';
MySQL
The MySQL database already has the crypto functions built-in, so reset the password with the following SQL statement:
UPDATE mt_author SET author_password = encrypt('the-new-password') WHERE author_name = 'USERNAME-GOES-HERE';
