The Stellafane Convention is a gathering of amateur telescope makers every year in Springfield, VT. Amature telescope makers from all over the world gather to share thier innovations, join in competitions, and enjoy the night sky.
It was started by Russell W. Porter in 1926, and is the longest running convention in the world.
The Riverside Telescope Makers Conference (now called the RTMC Astronomy Expo) is held in Big Bear City California. It is sometimes called the "Stellafane of the West". Another notable gathering of amateur astronomers is the Texas Star Party.