Sketching with Pencil
Evolus Pencil is an open source software for prototyping and sketching and is what I use as a free alternative to all the web based existing applications to do the designs and wireframes. It has many bundled stencils collections to use based on Android,iOS and many web frameworks components ...
Numix, not just yet another theme suite
Numix is a great project composed by many design artworks like icons and backgrounds to use on your Linux desktop distribution. The good design and taste of all of its elements converts your bored distribution into a beautiful pleasant for your eyes experience. And it also can be applied in your Android devices.