Butler is a Tcl/Tk panel of app-launching buttons. I prefer this to the one provided with most window managers because it allows me to include the X-selection in the command. In fact, I generally prefer to use fvwm's popup menus, and use the butler mostly for tasks which require knowledge of the selection.
Adam Costello is responsible for most of what is good about this program. He also has a newer version of butler on his site.
Things available here: