Although the actual documentation you get with many open source applications and platforms can feel paltry compared to what you get with proprietary alternatives, many book authors have served up free, online books on open source topics. We round these up on a regular basis here at OStatic, and in this post you'll find seven online books that you can get comfortable with quickly. They introduce essential concepts for getting started with Linux, Firefox, Blender (3D graphics and animation), GIMP (graphics), the OpenOffice suite of productivity applications, and more.