DPreview is a site for camera reviews and equipment. There is also a forum for discussing the different types of cameras, lighting, etc. There isn't a forum for ProShow, but it is a topic that occassionaly gets discussed in the PC Tools forum. Here's a link to the site:
DPreview
Other than the Yahoo Group, I'm not aware of any other forums that focus on the ProShow products. They may be out there, but I haven't come across any.
Mike