Need to build a scope fast? Really fast? Look no futher than these acolytes of John Dobson. Bringing Astronomy to the Man on the Street. See a sidewalk? It's an Observatory. Great people there. They also bring scopes to the public star parties at Griffith.
Another big group but a little to the south of us. Really nice facilities. Lots of good talks.
A really impressive astronomical society with active members and lots of neat stuff going on. These are the people that run RTMC.
This Society is big into outreach and public education. Nice website. They also have some really nice astroimagers.