The primary aim of the Gtk+2 panel project is to provide a panel that reuses whatever is available (if it is not overkill) in the obvious way, such as subclassing GtkWidget instead of implementing applets, or by using a GtkBuilder file instead of defining a new format to customize the panel. This approach gives some additional advantages for free: you can use common tools in uncommon ways. Above all, you can use Glade to design your own panel. All the dependencies apart from GTK+ are (and hopefully will be) optional.
MDIFramework provides a ready-to-use architecture to ease the creation MDI-style applications in Java. It takes care of the overall architecture of the main window of the application, with a tabbed architecture, the presence of an HTML printable message area, and so on. It provides a generic API to manage lengthy actions, keeping the interface responsive, and taking care that actions are performed one at a time, without having to bother about it. It can add metadata to already opened files. It manages loading and unloading of external plugins at runtime.