There are lots of digital circuit components noded on everything, some with very excellent functional diagrams.
In order to help gather this resource on digital systems, I've gathered the nodes here. I have also added links to components and writeups that do not exist, in order to provide a guide for further growth. If you have any corrections/additions, please /msg me:
Basic Combinational Logic
Multiple signal handling
Latches and Flip-flops
Adders and other mathematical components
Registers and Memory