SQL Databases

ADO Explorer
A tool that presents a explorer tree view of a database. By PEYO.
http://www.peyo-home.sk/adoexplorer/

CAST
Software for source code parsing, debugging, impact analysis, real time map building and evolution management for all client/server SQL based applications.
http://www.castsoftware.com/

Daffodil Software, Ltd
A embeddable, SQL-99 specification compatible, Java-based database engine. [Commercial and open source]
http://db.daffodilsw.com/

Data Transformations Inc.
SQL Query Tools available for download, and database consultation services.
http://www.datatransformations.com/

DataMirror Mobile Solutions, Inc. - PointBase
Java database for embedding within Java applications to manage and distribute data on servers, laptops, PDAs and other mobile devices. Supports standard SQL and JDBC, and can synchronize to back-end enterprise databases.
http://www.pointbase.com/

DBScribe
Documentation tool generating output in HTML, CHM and MS Word formats. SQLServer, Oracle, DB2, MySql and PostgreSQL supported. [Commercial, trial versions]
http://www.leadum.com/products.php?prod_type=DBScribe

DevGuru Intro to Microsoft JetSQL
40 page reference tutorial that explains and gives examples of code for Jet SQL clauses, declarations, expressions, functions, operators, and statements.
http://www.devguru.com/technologies/jetsql/quickref/jet_sql_intro.html

DTM SQL editor
SQL editor with ODBC and IDAPI support, visual query builder, syntax highlighting, and search and replace capabilities.
http://www.sqledit.com/

Frontline Software
FrontBase is a cross-platform SQL database with conformance to many international and de facto standards.
http://www.frontbase.com/

IBX Data Systems Ltd.
Creator of DBsurfer, an English query and decision support tool with a synthetic language interface that generates optimizable SQL for fast information retrieval.
http://www.dbsurfer.com/

Mimer Information Technology AB
MIMER is a SQL based relational database management system (RDBMS) targeted at mission critical client/server environments.
http://www.mimer.com/

Quadcap Software
The Quadcap Embeddable Database is a high performance pure Java database coupled with a JSP-enabled Web Server. QED supports Internet, intranet, and CDROM deployment of web applications.
http://www.quadcap.com/

Red Gate Software Limited
Supplies tools for SQL server database developers and DBAs for comparing and syncrhonizing databases.
http://www.red-gate.com/

YARD-SQL
SQL database system for UNIX from YARD Software GmbH.
http://www.yard-sql.de/