This list is incomplete, you can help by expanding it.
Adam Lavigne (and his blog) is a fantastic piece of work that I have been reading for years, and have even had the immeasurable displeasure of working with personally. The stories he tells color the trees he creates, and his penchant for using them to smuggle in useful lessons about styling trees mark him a masterfully cunning linguist. If only he was as keen on keeping his grimy mitts out of photos as he is on telling bad jokes.
The r/Bonsai subreddit takes the title of the first place I was exposed to bonsai outside of the Home Despot garden section. It remains an excellent source of both discussion and exposure to new resources, a fact of which you’re likely aware already if you’ve found yourself here.