A Community Wireless Network is best defined at Wikipedia. It's basically a group of like-minded people who got sick of paying telco's for high priced, and underperforming data links. Groups exist all over the world, and chances are that there is one right near you!
How do I find my local group?
If you are looking for a CWN in Australia, then you've come to the right place. Click here to start searching for your local group. If you are not from Australia, FreeNetworks.org is probably your best port of call to find somewhere close to you.
What do I need to connect?
This will vary from group to group, as well as how much you want to get involved. A simple client node may be nothing more than an access point and an antenna. A complex node may have three or more interfaces and be a central point for dozens of local users - and may even be hooked up to other major nodes. You should check with your local group to find out what equipment is recommended, where to obtain this equipment, and what configuration options are suitable.
If you are looking for help with a specific group or configuration for a group, then it is better off contacting that specific group. Try the groups web site, as most groups usually have a mailing list, or wiki where they give out specifics.