As a Photoshop/Lightroom user since version 1 I have seen and used many plug-ins and presets. Years ago I even purchased a book (like in paper and I have no idea where to look for that anymore) and purchased a few e-books.
While I find the majority of the plugins and presets to be overpriced and overhyped, and many publications often too shallow and repetitive, I have always enjoyed the tutorials from Julianne Kost. I usually find them to be useful, well explained and informative. The best part of it: they are free as well.
And while I’m just at it, you might be also interested the just published tutorial on toning black and white photographs as well. Will have to catch up with that one myself.