Talk on Open Source vs Proprietry databases

Hi

I have been volunteered to give a talk at a Linux conference 
(http://www.linuxafrica.co.za).

The context is the following

A Comparative Analysis of Opensource and Proprietry Database Technologies

Several options exist for selecting a database on Opensource operating
systems such as Linux and FreeBSD. This talk is geared towards allowing
a suitable choice of database to be made depending on the context of use.
The talk focusses on the technical differences amoung various database 
technologies.

Any pointers to existing material and references would be much appreciated.

Please respond directly to theo@flame.co.za

Regards
Theo

PS My choice is PostgreSql!