Rocket Lab and Relativity Space are also doing pretty cool work. Rocket Lab is the only other company to successfully reach orbit, they're the first to make an electric-pump fed rocket engine, and their upcoming Neutron rocket is supposed to be mostly reusable and does several things better than the Falcon 9. Relativity is using 3D printing to manufacture most of the rocket. RFA (Rocket Factory Augsburg) is also interesting, they're not doing anything novel AFAIK but they're using cheap parts from the automotive industry to bring down prices.