Great question to ask.
My top five building information sources are:
1) Google searches with the word "images" included in the search. I find seeing a picture of something is a quick way to find new ideas.
2) HomemadeTools.net - Encyclopedia of Homemade Tools
3) YouTube including about two dozen subscriptions and searching within each subscriptions
4) Emailing some of my favorite YouTube authors but keeping the questions short and to the point
5) I have a home library of books on using tools, tool catalogs, building techniques, etc. that serve as inspiration for ideas and building methods with lots of yellow stickies and sheets of notes stuffed in the pages.
I am also a member subscriber to Practical Machinist, Tool & Die Guy, Home Model Engine Machinist, and Mad Modder where I can find a variety of "how to" information, photos, and references.