I've been working on a web based tool to create database diagrams - aka Entity Relationship Diagrams. While I've had some success, I also have run into some issues. Tonight while I was browsing the web I came across Mogwai ERDesigner NG. This project has many more features than my simple application does, and most importantly to me at the moment is the ability to connect to an existing database and reverse engineer it to come up with the diagram. This step is a HUGE time saver when you are dealing with large databases.