Databases

• MiniSQL (aka mSQL) and manual, plus feature list, W3-mSQL. Contributed software for this includes JDBC driver and documentation.
• There's also MySQL and FAQ. This is another free SQL implementation, with a similar API to mSQL. There is a JDBC driver for MySQL. The MySQL docs contain a section on SQL and a sample database and tutorial.
• PostgreSQL: Evaluating postgreSQL for a Production Environment, a comparison of 4 databases
• Tutorials: SQL tutorial which contains some links to other resources, including a brief tutorial at NIST in the US. Further links at the SQL reference page.
• Australian list of database programs