The Hullabaloo
It was our board back in the days when there was a SimsHost. The site is available for reading but I took out the software that enrolls new users because I can't keep up with maintaining so many boards. The Hullabaloo uses phpBB and I like the vBulletin software that Sun Sims uses, so here we are!
If you're thinking of building a railgun kind of launcher, mountains won't help much. Even at the peak of Mt. Everest, if you were accelerate a payload to orbital velocity and let it hit the atmosphere, the theoretical stagnation temperature would be over a million degrees. (Never mind what temperature scale you use to measure it. You'll have a plasma of disassociated atomic particles long before you get up to speed.)