I want to present an online
dbdsgnr database schema
generator . The service is made on python and google app engine. Logging into it can be having an account in Google. Briefly about the service: you draw a database schema, and the service gives you code. At the moment, you can only get it for MySQL, but they promise support for PostgreSQL, SQLite, MySQL, MSSql, Oracle. Under the cut an example of working with this service.
To begin, create a table by clicking on the appropriate button and giving it a name.

Then we create the fields in the table. A field can be either a simple type or a link to another table if we already have several of them.

When everything is ready, we give our schema a name and save it.

After that, click on the magic button
sql and the code in front of us.

Profit! In my opinion, quite an interesting and visual tool.