>Would you know of a website that would be a good higher-level starting point for learning about DNN?
>

Hi Jon,
DNN is have just ready barebone. You can develop your own custom modules or customize moduse developed by some other from DNN comunity - there is more than 200 ready modules most of them freeware, others is shareware - with price less than $50.
And here comes role of designers - Most famoust which have its own website is from Australia. I work with France and Romanian one. They make skins and module containers.
What is more important if you are .Net developer - to undestood philosophi of the portal which will let you to customize modules or develop your own one.
It is easy to download DNN and to review its code. reviewing code of a few modules you will be able to understand rules how could be developed custom module and how it could be prepared for upload in DNN
HTH