As moderators come and go, there's elections every so often where the existing staff will consider applications from the users for the position of forum moderator. Every so often, the senior mods do the same thing, picking people from the moderation staff who rise to the higher standard of responsibility (senior staff are effectively moderators of the whole site). And once in a blue moon the admin staff will pick someone from the longer-serving staff and Sr. staff to join their ranks too - although usually this process is not quite so public.
There are also a couple of engineers who lurk behind the scenes keeping the computers that host the site from falling into the hands of Elbonian spam gremlins, too. They deserve as much mention as the rest, I'd say.