There are e-mail discussion lists for almost all topics surrounding KDE. An overview of these lists can be found here.
Particularly the kde-devel mailing list is of interest to everybody who want to develop KDE-based applications or want to develop for KDE itself.
Please keep in mind that all these lists are largely driven by volunteers - demands and threats are sometimes met with cynicism and rejection, while technical questions and legit criticism is usually dealt with quickly and nicely.
If you need guaranteed response times and business level support, there are several options to chose from:
A list of companies supporting KDE can be found in KDEs Business Directory.