Gtk2::Notify does what I want - gives me popup text to let me know when stuff happens. I use it in a music player and in a little executable wrapper that informs me when a task is done. At one line of code per popup, its hard to beat.
The docs and interface are automatically generated, so they aren't fantastic by any means. Since the API is an exact match with the GTK+ API however, there's plenty of examples out there on the web.
At the end of the day, it does the job without being a complete pain, so its recommended.