Database Directory
Provides short descriptions of the several popular RDBMS. Features various database articles.
http://www.databasedir.com

SQL Tutorial
SQL tutorial featuring comprehensive guide to SQL language concepts and SQL commands.
http://www.sql-tutorial.net

TabTag
TabTag is the only product that links Microsoft Outlook to the full power of a SQL database. Writing Outlook data directly to accessible SQL Server tables, TabTag is suitable for any database size.
http://www.tabtag.com/