This is from a month or so ago, a procedurally generated galaxy rendered in OpenGL. No extensions - just basic texturing and vertex colours!
The background is two cloud layers (the blue and the purple) which are cellular textures. These expand from the edge outwards to give a swirling effect. Vertex colours fade these out nicely.
The arms are also cellular textures, but with the intensity reversed. These are basically a long strip bent around in a circlular arm. Again, animated via messing with the texture coords and vertex colour fade out.
The stars are all just sprites which orbit at different speeds, with random sizes. Central flares are just static geometry, and theres a (very subtle) central glow which makes the core look nice and firey.