Another currency forum that has very active currency discussions is a site run by PCGS. Their topics are on a wide range of currency threads. This site can be viewed with the following link.
Collectors Universe Forum
A third currency forum is operated by PMG but it is not highly used. You can check out this site with the following link
Collectors Society Forum
With all three forums, you will have to join to be able to post comments on their sites. Membership is easy to do and is well worth the effort.