New on Dzone.com today they've posted the third and final part of their series looking at lesser known databases systems you might want to use in your application. In this latest article they cover eXist DB and Hypertable.

Welcome to the third and final part of the series in which we look at five alternative databases you can use with PHP apps you might not have heard of. [...] In this final part of the series, we’re going to finish up by looking at two outstanding, yet markedly different, databases: eXist DB and Hypertable. So let’s get started.

As in the other two parts of the series, they include a brief overview of what each database is and some sample code showing it in use (and what you'll need to install to use it).