Guile-Clutter has a mailing list, which for historical reasons, still is the one that was created and used for the Guile-Gtk project. Please send us your questions, patches and/or requests for improvements there. You may subscribe, unsubscribe and read the archives here.
Guile-Clutter currently shares its bug tracker with Guile-Gnome. You may submit bug reports using the bug tracker or, if it's easier for you, using the mailing list.
You can sometimes find some of the hackers hanging out on #guile on irc.freenode.net.