Paul Breed's Unreasonable Rocket, the dark horse (and my favorite) of the X-Prize Cup's Lunar Lander Challenge, is still pushing the envelope of real amateur rocketry. I had seen that he has been working with 3-D printed bi-prop engines but now see that he planning multi-engine, multi-stage, OTRAG-style space launch vehicle. You can get a nice overview of this project from his presentation at Space Access 2016. Pretty ambitious for a self-funded project! IIRC, his LLC team was mostly just he and his son. So, ambition and tenacity has never been a problem for him.