Remember Gnome2 Global Menu? It's an applet that adds a global menu (the menu is displayed on the top panel) for Gnome 2 that wasn't very active for a long time because Ubuntu built its own global menu. But it's back!
Gnome Global Menu is currently being ported to GTK3 and an alpha version is already available for download so you can get a global menu in GNOME Shell. Here's a video with the new Gnome Global Menu running in Ubuntu 11.10 (with GNOME Shell):