OLEDB  
   A class library used to open a Microsoft Access or SQL database. [Open source]
   http://www.thesett.co.uk/swdev/

freeodbc++  
   A C++ library for accessing SQL databases. Designed with standards in mind, so it provides a subset of the well-known JDBC 2.0 and runs on top of ODBC. [Open Source, LGPL]
   http://orcane.net/freeodbc++/

MetaKit structured storage  
   Highly portable, lightweight database manager, usable from several languages.
   http://www.equi4.com/metakit/

ODBC Broker  
   C/C++ library to access ODBC data sources with only a few lines of code. Now, make dynamic database engines to access any ODBC data sources without knowing about ODBC!
   http://www.sqldata.com/broker.htm

Database Template Library  
   Provides ODBC recordsets just like STL containers, including writing the contents back to the database.
   http://dtemplatelib.sourceforge.net/index.htm

OTL  
   Oracle, Odbc and DB2-CLI Template Library. A set of classes that wrap around the dynamic database programming interfaces of Oracle, DB2 and ODBC. Also provides support for block-updates and other caching mechanisms.
   http://otl.sourceforge.net/

MySQL++  
   A C++ API for MySQL. Tries to make working with queries as easy as working with other STL containers.
   http://www.mysql.com/downloads/api-mysql++.html

AccessLog  
   A C++ wrapper to give an XBase fashion to the Berkeley DB library.
   http://www.geocities.com/lpiergentili/accesslog.htm

OSQL  
   Discusses a wrapper for the Oracle Call Interface including source-download.
   http://codeguru.earthweb.com/mfc_database/Osql10.shtml

Ora++ Library  
   A set of C++ classes wrapped around the Oracle Call Interface (OCI). They provide an object-oriented interface to Oracle similar to other OO interfaces like JDBC or PERL.
   http://mywebpages.comcast.net/jimcainadmin/orapp/

ORA++  
   OCI C++ Interface Library. Download, sample applications, bug tracker.
   http://orapp.sourceforge.net/

C++ ResourcePool  
   An abstracted C++ database API with advanced transaction management and reliability features. [Open source, GPL]
   http://www.fatalmind.com/software/ResourcePool/cplusplus/