The Verve panel plugin is a comfortable command line plugin for the Xfce panel.
It supports several nice features, such as:

     * Command history
     * Auto-completion (including command history)
     * Open URLs and eMail addresses in your favourite applications
     * Focus grabbing via D-BUS (so you can bind a shortcut to it)
     * Custom input field width

WWW: https://goodies.xfce.org/projects/panel-plugins/xfce4-verve-plugin