SQL

Archive of SQL Examples
Site provides basic SQL syntax as well as query optimisation tips for various database management systems (SQL Server, MySQL, Access, Paradox).
http://amper.110mb.com

Archive of SQL examples
Free archive of source code examples for SQL programming for various database engines
http://www.sqlexamples.info/

JCC's SQL Standard Page
A source of information about SQL standards.
http://www.jcc.com/sql.htm

SQL Dumpster
Free SQL scripts for website and application developers.
http://www.sqldumpster.com/

The SQL Summit: Understanding SQL/XML and Information Retrieval
Portal site with information about databases, SQL/XML, XQuery, modeling, information retrieval, and web and grid data access. Includes articles, papers, and audio and video programs.
http://www.sqlsummit.com/

SQLinForm
A free web-based Java tool to format any SQL statement independent from their Database. It can also prepare SQL statements for Java, C#, VB, ASP.
http://www.sqlinform.com

UESQLC (Universal Embedded SQL Compiler)
An embedded SQL-92 precompiler for C++ and Java, designed to be extensible using SGML documents. [Open source, GPL]
http://www.uesqlc.org/

W3 Schools' SQL Tutorial
Useful SQL language reference for beginners and experts alike
http://www.w3schools.com/sql/default.asp