Without knowing what your member association is/does, I can't give you a clear answer. I can tell you that Twitter would be a great way to attract new members if Twitter is a tool that people in your industry/field use.

As nlowell points out, you should figure out how people are using your website first, before putting it out on Twitter. If you have tons of content, but it's not engaging, Twitter isn't going to help you. However, if you have a thriving source of info, it could be helpful to potential members to see this constant instream of new information.

My word of advice is don't overload on Twitter. There are people I've stopped following because they post too often and jam my feeds with duplicate or similar tweets, which is annoying. Create balance with what you're putting out there.

Good luck!

JMO, but unless twitter has a significant penetration into your membership, that would be a waste of time. For it to be useful, you have to have people follow you and if they're not there to begin with, it won't help.

We have this problem in our membership organization as well. Our content is not available through RSS feed, and when it is updated, the only people who are excited to see the change are the people who posted the content and the association management.

If you want people to come to your site, it has to be relevant, interesting, and accessible.

So? What's on your site? If the membership isn't visiting, it's because they don't know it's there, or because they find it of limited value. Fix those.

The other question to ask is what it means to be a "member association" in the current context. when the only way to find people active in your field was to join one, they made sense. That rationale disappeared about 2002.