The purpose of Xhotkeys is to provide a simple and easy
configurable hotkey launcher for the X-Window System. It should
work on all desktops (Gnome, KDE, Xfce, ...), and you can still use
their own hotkey launchers. Although Xhotkeys has a graphical GTK configurator, it's possible to manage the configuration file manually.
The source code and binary packages for Debian (so, works also for Ubuntu) are available.