For all general documentation regarding the Omega2, the docks and expansions, general tutorials on the Linux operation system and programming languages supported, …. and of course, the Onion Console IDE.
Project Book, Vol 1
The Onion technical team has created a whole project book, filled with step-by-step guides to a variety of basic, IoT, smart-home and communication design projects for your to build and hack with. You can download the free book here.