GTK+ now contains the old BaconVolume widget, called GtkVolumeButton. I hope we get GTK+ 2.12 for GNOME 2.20, so that Rhythmbox, Sound-juicer, Totem, Banshee, etc. can use the widget without cut'n'pasting bacon-volume.[ch].
Many thanks to Ronald for writing the widget in the first place, and Matthias and Christian for the code reviews.