If the 301 redirect is applied correctly, you should see the subdomain either be added or removed (depending upon your pre-set standard) when the opposite version is used. Try entering the netbuilders.org address without the www subdomain and you will see what I mean.
Another canonicalization issue that I didn't mention has to do with Microsoft servers. File names and paths are not case sensitive on Microsoft servers (they are cases sensitive on Unix and Linux servers), which allows sloppy programmers to use multiple versions of file names in hyperlinks with an improper mix of upper and lower case characters. In other words, ContactUs.html, contactus.html and CONTACTUS.HTML are differnt file names on Unix and Linux, but represent the same file name on Microslop servers. Google and Yahoo run on Unix and Linux, so if non-standardized and inconsistent capitalizations and case are used in hyperlinks on a Microsoft servers, G and Y can sometimes see them as different URLs and create another form of duplicate content. If you are on Microsoft server, it is important to use the exact same versions of paths and file names as they exist on the server.