I use BigTent and through that I'm on The Mother Connection. It's extremely helpful and a great resource. They have a calendar if local activities and deals, a classifieds section, forums etc. TMC focuses on moms in the Merrimack Valley. I myself live in Andover but its extremely helpful for anyone north of Boston. I've met some great friends through it as well!
I also use bigtent in the Boston area, but that can be sort of slow too. I know that fb often has groups. I would even start your own! My friend did that for the south shore and a bunch of us invited other mothers we knew so there's a great network on there.
Re: Boston forums/community websites
[MC 11.20.11] [DS born 9.24.12] [DD born 10.15.14]