Here's my experience with a couple of local Chambers FWIW.
I joined a Chamber of Commerce through my "day job" (family business/non writing job). I'll call it Chamber #1.
They had a "monthly newsletter" that appeared about two times each year, so I volunteered to take it over. In the course of a couple of years, I got the newsletter on a monthly schedule and moved it into the computer age (we started off doing it on a typewriter with a little press type and paper clip art and photocopying it--we were eventually able to get a deal from one of our printer members to do the layout and printing).
A few years later, I used clips from the Chamber #1's newsletter to land a steady freelance gig as a business writer for a local newspaper (there was a method to my madness in taking on the first thing as a volunteer gig--besides, being a Chamber #1 member was part of my "day job" duties).
Writing for the newspaper was a part-time gig that job lasted nine years. The newspaper eventually expanded to a little chain of five weeklies, and I wrote articles for all five papers.
The publisher of the newspaper knew of my prior experience writing for a local Chamber. He was also on the board of a neighboring Chamber (Chamber #2 <g>). When Chamber #2 lost the person writing their newsletter...he recommended me.
That one was a paying job, and I wrote for Chamber #2 for several years.
Currently, I'm a still a member of Chamber #1 (I'm still with the familly biz)...and I joined Chamber #2 (which happens to be in the town where I live)with my freelance writing biz.
I go to some of the after-work mixers (I was a Chamber board member for Chamber #1 for about 10 years...time-consuming, so I've pretty much just stuck to going to "networking" events with Chamber #2).
I've gotten a couple of referrals for one-shot press release jobs from Chamber #2. There are several other writers in Chamber #2, and there really isn't a lot of work in the Chamber for any of us.
I did get some decent story leads by going to mixers and meeting people when I was still with the weekly newspaper. I also did a front-of-the-book type piece for a national market for young business owners about joining the Chamber.
I write for a monthly glossy now (mostly advertorial fodder, which pays the freelance biz bills) and do press work for a local dinner theater...so I don't really get many useful leads at mixers these days).
Working directly for Chambers isn't particularly lucrative in my experience, either. Like a lot of smaller non-profits, the pay is on the lower end of the scale (when they're not trying to get volunteer word), leadership sometimes changes frequently and they struggle trying to do more in-house or with volunteers when finances get thin.
I've kept the membership in Chamber #2 primarily to keep up on what's going on around town. I put it on my resume as well.
Bottom line--I'd say my experience was mixed. I've made a bit of money and gotten a few leads through my Chamber associations, but not always enough to justify the cost every year. Overall, I've still made a little more money than I've spent on memberships over the years. I like knowing what's going on around town and keep the Chamber #2 membership primarily as a point of pride right now.
YMMV
