A few weeks back I made a logo for a friend's Soundcloud.com music project, Root Node.

We wanted something simple that would look good as a small thumbnail image. The concept was a more literal node tree than we see in Blender's node editor. My friend gave me a doodled sketch, and I re-created it with Blender and threw in some compositor effects. I recently shared it in the Blender NPR facebook group, and enough people were curious about how it was made that I will share the settings and file.