I'm the author of Trello Dojo https://leanpub.com/trellodojo Marketing does not come naturally to me. I feel like it's a good product, but I don't want to be spammy. By far the best marketing choice was to ask Trello to put it on their resource board. I was so nervous- what if they didn't like it? What if they sued me for trademark infringement or something? They did none of those things and put it up cheerfully, where Google Analytics says a majority of me references come from.