The official Quest3D wiki was opened not too long ago and can be found here:

Quest3DWiki Main Page

And the video tutorials made by VSTEP can be found here, they are based on Quest3D 3.0:

Video tutorials

And, just for your convenience, a quick link to the reference manual with all the channels. It is still being worked on at the moment by Peter Wuyts, but there are some noises at the Quest3DForum about allowing other users to add content as well.

Reference Manual/Channels