Language Bindings
Ruby, Bakery, ggwydiondylan, Gnocl, Gnome Language Bindings Matrix, Gnome-GCJ, gnome-objc, GnomeHaskell, Gtk-Perl, gtkmm, guile-gtk
Interface Design - Menubars
Article - from a UI Design Perspective - about configuring Gnome to use a Single Context-sensitive Menubar, instead of multiple redundant (one per window) Menubars.
The Official GNOME development Manual
This is the entire GTK+/Gnome Application Development manual. It is available online in its entirity and is always up to date.