Learning to Use Manakin (XMLUI) - Overview of how to use Manakin and how it works. Based on DSpace 1.5, but also valid for current versions
Making DSpace XMLUI Your Own - Concentrates on using Maven to build Overlays in the XMLUI (Manakin). Also has very basic examples for JSPUI. Based on DSpace 1.6.x but also valid for current versions.