Writing Sublime Text Plugins is a new book by Josh Earl. I bought it and think it’s a great place to start if you want to learn how to make Sublime Text do more. I’d recommend it even if you don’t want to make your own plugin to distribute. If you’re like me, you might just want your own function that does something special to you but useless to almost everyone else.
Writing Sublime Text Plugins starts with the foundation you’ll need. There’s a lot of detail in it that is easily missed in a short tutorial. This thing is almost 35K words, so it probably covers most of what you’ll need.
A minimum of $22 on Leanpub.