This software automates the process of creating schemas in OmniGraffle using MySQL databases through an Applescript.
Once all your tables are drawn, db-schema2omnigraffle uses Omnigraffle's auto-layout feature to arrange your tables on the canvas. Though this may not always be ideal, keep in mind that you'll likely modify the drawing to suit your needs anyways.
Overall, the script doesn't just create table drawings. It also identifies connections using Martin Fowler's Active Record Pattern, which is used in Ruby on Rails and other projects. So if you're looking for a software that simplifies your database schema visualization, db-schema2omnigraffle is worth checking out.