User's Manual
The User's Manual contains a description of the entire UI and some rendering guidelines. It also contains the API documentation.
Video Tutorials
A series of six tutorials (along with Maya scenes) created by Paolo Berto give a good overview of some of the features found in 3Delight for Maya.
Release Notes
All release notes since the release of version 2.0 in May 2006.
License Server Guide
This guide explains how to obtain and install the license key and start the license server. Note that this is not necessary for the free version.