gtkmm's gtkmmproc system makes it quite easy to create gtkmm-like wrappers for any GObject- or GtkWidget-based API.

gconfmm and libgnomecanvasmm have been API stable for a long time, and are in common use.

gnome-vfsmm has been started and seems very useful. It is making good progress and I see no reason why the API shouldn't be stabilised after a few months.

libgnomeuimm is not yet API stable because its dependency, libbonbouimm is not API stable, partly because orbitcpp is not stable, because orbitcpp is difficult. Luckily, there is nothing very useful in libgnomeuimm. If anyone actually needs it, we will happily release a stable libgnomeuimm version, without the libbonobouimm stuff, and work on a development branch.

Gergo Erdi and now Bowie Owens are making surprisingly good progress with orbitcpp - but we don't know how much more work there is to do. You should help, and if you don't care enough to help then you probably don't need it. You need it to write Bonobo controls, but not many people need to do that.