Postgresql AutoDoc is a utility which will run through PostgreSQL system tables and returns HTML, DOT, and 2 styles of XML which describes the database.
protosquared is a "data server prototype". It supports several data sources, such as XML and SQL databases and the communication protocol is highly configurable too.
Glom is a GUI that allows you to design MySQL table definitions and the relationships between them. It also allows you to edit and search the data in those tables.
SafeSQL is an SQL query processer to automate the tedious tasks of syntax testing, injection attack-proofing, dropping parts of queries and other misc features.