A simple introduction to working with LVM - An brief howto on the concepts of logical volumes and working with Logical Volume Manager to manipulate filesystems in linux.

Programming Ruby: The Pragmatic Programmer’s Guide - Also known as ‘the pickaxe’ this is the free online version of the ruby bible.

Whys (Poignant) Guide to Ruby - A surreal tutorial introducing and explaining ruby particularly it’s syntax and some of the aspects which differentiate it from other languages.

Gruff Graphs for Ruby - A library to easily make very pretty graphs using ruby.

Colour Illusion Tutorial - A tutorial on how to make the mind see colour in a black and white image via illusions like this Spanish castle.