Our PTO has had the same problem -- only a few parents (mostly board members) showing up at meetings and running everything. Although the parents who weren't involved share some of the blame, much of it had to do with the president, who didn't seem to want to allow anyone but her "inner circle" to do anything.
There was also virtually no communication with members (other than a notice of meetings on the district calendar and the sign board outside the school). Anyone who did not or could not attend meetings was completely out of the loop, and if they questioned anything or tried to raise new ideas, they were told, "Business is conducted at the meetings" -- in effect, members were punished for not attending. The meetings were horrible, too -- even with the small group (board members and two or three regular attendees), no one would welcome a newcomer or even introduce themselves, and there was no room on the agenda for members to raise questions, suggestions, ideas, etc.
Things have changed a bit, and this coming year we are expecting to have a whole new executive board, of which I will probably be a member (I am running unopposed, but you never know!). Here are some of the ideas I hope will change things for our organization (all learned from painful experience!):
1. Communicate with members! Ask for e-mail addresses (and permission to contact by e-mail) with the initial membership packet. Set up an e-mail list of all members (be sure to hide addresses when you send e-mails, just to ensure privacy). Send e-mails out announcing meetings -- with the agenda and previous minutes if available -- and send out a call for agenda items. Send out requests for volunteers whenever an event is coming up, too! Have a return e-mail address so people can respond. ANSWER ALL E-MAILS!
2. Set up a webpage that links into the school page. Post minutes, agendas, important dates, volunteer opportunities, interesting articles, links to local newspaper stories about students, etc. Be sure to maintain the page, and update it frequently! Have a "contact us" link to the e-mail address, and again, answer all e-mails!
3. Make members feel welcome at meetings! Greet them when they arrive. Find out what they can offer and what the organization can offer them. Have a place on the agenda for members to speak, and encourage them to share ideas about events and regular business. Have coffee, tea and cookies at the meetings!
I hope these changes help to increase our volunteer lists. I'm not so concerned about meetings -- I think people should come if they can, but they should not be punished by having no voice in their organization if they can't attend meetings.
I hope these ideas are useful to some of you, too. I will let you know how it goes. If you have ideas for me, I'd love to hear them.