Simple Machines Forum is lightweight and patched quickly. You can update the core files and install plugins from the admin interface. It also has a nice plugin to work with Project Honeypot to identify and stop spammers. I like it better than PHPBB, way better.

Another approach, instead of a blog or forum, is a simple guestbook script for comments. It's not threaded like a blog or forum, but it's an option..

That would be SMF Forums which are really nice and pretty easy to setup.

This is great, ideas coming in thick and fast. I'll look at them all......trouble is I have to consider what is best for the Society.

One possibility, if you want a blog, is to set one up in WordPress. Here is even a free course to get you started: http://courses.sitepoint.com/gettingstartedblogging