Yahoo refers to forums as groups; each group is generally topic specific; expert assistance may be available at such groups when not available at site such as T2W, and sometimes not.
Yahoo Search will display most but not all listings eg: MetaStock tho Torontometastockusers isn't in the list; Searches may have to be done by Category since groups may not identify their topic by their name; sometimes the group name must be known in order to access that group.
Microsoft and others have similar group/forum collections plus more individual sites are today adding their own forums.