Callback Framework for C++
There is a mailing list, libsigc-list@gnome.org for libsigc++. To subscribe, use the web page.
Members can post directly, but all other traffic is moderated. There is an archive of messages, here.
Please report bugs as GitHub issues, or provide improvements as GitHub pull requests.
The libsigc++ source code is in the libsigcplusplus repository on GitHub.