I've got two big projects coming up where I'll be using Unity to make a 2D game. Because of this, I've naturally begun looking into Unity tutorials. Though I have some experience with the engine from the Scottish Game Jam and my team's game Denizen Pop, I still have a lot to learn.
To that end, I've started going through the 2D Unity tutorials by Tim Miller of Rocket 5 Studios: http://www.rocket5studios.com/tutorials/make-a-2d-game-in-unity3d-using-only-free-tools-part-1/
So far the tutorials have been excellent, and have introduced me to a lot of great, free tools I would otherwise never have found. I definitely recommend them to anyone learning to use Unity for 2D game development!
I don't have time to write an in-depth article today, but I hope to post later this week with an update on my team's progress with our game Pollinator: Flower Defense.