Nick Hodge has recently set up a new peer-to-peer forum with Blogs, Forums and File areas for Excel users.
For more information and member registration please see: Excel User Group
What makes it attractive is that it has an Add-ins subforum:
This subforum will discuss and also be a Q&A forum for:
COM Add-ins created with VSTO (and also about workbook level solutions + templates.)
COM Add-ins created with C#/VB
COM Add-ins created with classic VB/C++
Automation Add-ins created with classic VB/C++
Automation Add-ins created with C#/VB
XLLs (Add-ins) created with C++ and C/C++
The subforum also covers deployment of all the above add-ins types.