Well, this looks pretty darn interesting. I don't have a lot of time to play with this, but SchemaBank, if it delivers on its promise, looks like a very useful ERD tool at a pretty reasonable price point.
You can export a SQL dump from MySQL or PostgreSQL, import this into SchemaBank, and start going. Or you can start with a fresh schema. You can do visual data modeling, versioning, branching, diffing - in other words, both modeling and change control for your schema.
The UI looks sweet, although I'd be curious how it handles super-large schemas, always the bane of ER tools. It does have "Bird's View" which is a good sign they're thinking in the large.