The main parts of Joomla 1.5 on two A4 sheets. That's the db8 Quick Reference Guide for Joomla 1.5. This Quick Reference Guide describes Joomla 1.5 in a nutshell.
The main parts of Joomla, a diagram of Joomla's organization of content (in Sections, Categories and Articles) and the presentation (in Menu) of that content.
This Joomla 1.5 Quick Reference Guide is available as free download. At the bottom of this article you can select a Dutch or English version.