ERCreator Database Edition is a price-competitive and productive ER-Diagram tool.
Diagram Ring is an open source advanced diagram editor.
Visual Paradigm International Ltd.
VP-UML Community Edition (VP-UML CE) is a free UML drawing tool.
It is designed for speeding and easing the database schema creation.
Free Software Foundation, Inc.
The FMC Stencils are templates and extensions for Visio or OpenOffice Drawing.