Draw Model from existing DB

I have an existing PostgreSQL DB and I would like to draw a model of the DB
structure. Is there some software (Freeware) around that can read the
existing structure of my DB and automatically draw e.g. an ER-model of that?
The software that I have found so far (e.g. Open System Architect) seems to
be able to build models from scratch and convert them into a DB, but not the
other way around like what I need.

I have found SQL Power Architect to work pretty nice in some situation. To get a model you simply create a new source connection to your db, connect to it and drag and drop it on to the playpen area (the right hand side in the UI).

There's both a community edition and a commercial edition. Project page is http://code.google.com/p/power-architect/

Regards
roppert