Yay! Happy to know that MSDN Forums now have an exclusive category for Office Development. Might be late yet useful. So, posting it here.
Microsoft Office for Developers – http://social.msdn.microsoft.com/Forums/en-US/category/officedev
It has separate wing for Outlook, Excel, Word and Access.
- Outlook – http://social.msdn.microsoft.com/Forums/en-US/outlookdev/threads
- Excel – http://social.msdn.microsoft.com/Forums/en-US/exceldev/threads
- Word – http://social.msdn.microsoft.com/Forums/en-US/worddev/threads
- Access – http://social.msdn.microsoft.com/Forums/en-US/accessdev/threads
In addition to these, there are two other wings.
- Innovate on Office in which the developers can suggest needful features and discuss on them
- Open XML Format SDK for discussing OpenXML related issues