The Raspberry Pi Foundation just announced that after two years of production, the VideoCore IV 3D graphics engine on the Pi has an open specification. This is pretty huge news — the Pi has required a binary blob graphics driver that runs on the multimedia coprocessor with a thin “open” shim over it on the main CPU since its inception, which means that its graphics stack was, for all reasonable intents and purposes, entirely closed.
The shim between the primary kernel and coprocessor drivers was open-sourced in late 2012, which was also a huge step forward; it allowed non-Linux operating systems to be ported to the Pi with some hope of usable performance. Since then, ports of numerous systems such as Plan 9 and the BSDs have appeared on the Pi. It's not yet clear (to me, at least) what direct effects opening the GPU-level graphics drivers will have, but certainly the philosophical value is enormous.
Here's to the Pi, a happy second birthday, and the next two years of openness and improvements!