The biggest advantage to being a member of your local chamber of commerce is "schmoozing" with other members. You have to let them and the other members in the community know you exist. I've been a member for about 6 years now and on the board of directors for 3. I'm also the webmaster for the chamber's website and one of the newsletter editors.
There are 5 other electrical contractors that are members but I'm the only one going to meetings. Why ? Some of the chamber members include 14 GC's, 5 plumbers and 8 real estate agents to cite a few. I'm not saying I get all their work but the amount of work that I do get and the referrals are priceless. It's hard to put a price tag on the actual work but I'd rather have the work than not.