Check out the schedule on the link in my sig.
Probably the best attended public programs are the tuesday/thurs interval sessions (typical session is described in one of the links)-- about for a couple months before the road season starts we'll get as many as 80 people. I don't do many of the wide open sessions, but they get ok turnout. There are some pretty good kids programs (links also on the website), and then various elite sessions and closed sessions for riders and teams who rent out the track.
One of the things that helps run things is getting clubs to recruit and organize volunteers for the big events, and in return all the club members get a 50% discount on track time. Plus it's fairly cost effective for a club to hold a closed session- if they can get 25 or so riders to show up I think it ends up being less expensive than a regular session, and new members can get certified to ride the track while other members help them and get in some riding time (those sessions don't show up on the schedule).
As far as benefit to the community, it's a great lifetime sport because it's pretty low impact (as long as you aren't mass start racing) and given the amount of infield time you always get, it helps people to meet each other while they aren't totally out of breath.