If you want to learn using the Unity game engine, and you know German - check out Jashan's book: Das Unity-Buch.

If you are a game developer using Unity, you might be interested in these tools that either already are or will be published to the Unity Asset Store:

• Score Flash: Let your players know what they've achieved - be it scores or collected power ups or achievements; or instructions in a tutorial. Whatever you want to put "in their face": ScoreFlash lets you do it in a fancy way. And the best thing about it: It's so easy! All you need is grab the prefab, put it into your scene and where ever you want the player to know they've done something awesome, just write: ScoreFlash.Push("Awesome!"); Yes. It's that easy! Now available: Buy Score Flash on the Unity Asset Store!
• STUUI - Skinning and Templating for Unity UI (fka uGUI): STUUI is a simple, yet powerful way to add skins / templates to your Unity UI  GUIs. It's so flexible that you can even use it for localization! The original idea was to have a central place to store certain color values that could then easily be changed without having to run through each every single Graphic-component in your GUI in every scene of your game. But to make it a complete solution, more features were added. More info on STUUI - Skinning and Templating for Unity UI (uGUI) on the Unity Asset Store