http://sqlrelay.sourceforge.net/
SQL Relay is a persistent database connection pooling, proxying and load balancing system for Unix and Linux.
SQL Relay is ideal for:
speeding up database-driven web-based applications
enhancing the scalability of database-driven web-based applications
distributing access to replicated databases
throttling database access
accessing databases from unsupported platforms
migrating applications from one database to another
SQL Relay supports the following database backends:
Oracle
MySQL
mSQL
PostgreSQL
Sybase
MS SQL Server
IBM DB2
Interbase
Sybase
SQLite
Lago
ODBC
The SQL Relay client API's support advanced database operations such as bind variables, multi-row fetches, client side result set caching and suspended transactions. SQL Relay is has native client API's for the following languages:
C
C++
Perl
Python
PHP
Ruby
Java
TCL
Zope
SQL Relay provides drivers for the following database abstraction layers:
Perl DBD
Python DB
Ruby DBD
PHP Pear DB
An application coded using another database's native client API may be able to use SQL Relay without modification. SQL Relay provides drop-in replacement libraries for:
MySQL
PostgreSQL
SQL Relay also features:
command line clients
a GUI configuration tool
extensive documentation