Theres a volume changer plugin for the panel available. Its name is 
xfce4-mixer.
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Numerous plugins are available for the Xfce panel from the Xfce Goodies 
Project page : http://goodies.xfce.org
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You can move windows between workspaces by simply dragging them in the 
pager applet.
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You don't want that new windows and maximized windows cover some area 
of the screen? Just use the "Workspaces and Margins" component in the 
Xfce Settings Manager to customize the desktop margins.
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You can use some keyboard shortcuts to start applications. To do this, 
you can use the Command Shortcuts section of the keyboard shortcuts 
editor available in the window manager settings dialog.
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There is a hidden option that allows the panel, and apps such as 
Gkrellm, to be included when you switch the focus from a window to 
others using the Alt+Tab shortcut. Just edit your 
$HOME/.config/xfce4/xfwm4/xfwm4rc (or create an new one) and add this 
line:

cycle_minimum=false
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You can disable the the ability to move and resize windows using the 
Alt button + mouse click shortcut. Just edit your 
$HOME/.config/xfce4/xfwm4/xfwm4rc (or create an new one) and add this 
line:

easy_click=false
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You can change the mouse menu that appears when you click the desktop 
background by using the graphical menu  editor available from the Menu 
tab of the Desktop settings dialog.
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The background settings dialog allows you to create a list of background
 images that will be randomly used when xfdesktop starts.
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There is a notification area available for the panel. 
You can find it in the items dialog of the panel.
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You can start xfrun4 (the application launcher dialog) with the Alt+F2 
keyboard shortcut.
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To learn more about Xfce 4, you can visit Xfce official website : 
www.xfce.org
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Just run xfhelp4 to open Xfce 4 manual in Mozilla.

You can change that to use your browser of choice by setting the 
$BROWSER environmental variable. For instance in your ~/.bashrc put the 
following line:

export BROWSER="galeon -w"
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The xflock4 script is used by the panel to lock the screen using 
xscreensaver if available, and falling back to xlock.

Just click on the "Lock the screen" system button of the panel, or use 
the Control+Alt+Delete keyboard shortcut to execute xflock4.
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The xfterm4 script is a convenient terminal script that uses the 
$TERMCMD environmental variable as terminal command if available, and 
falls back to using xterm.

Especially useful in the panel where you can drag file or directories 
to it that will be viewed by the appropriate console application (less 
for text files, lynx for html).
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The "xfmountdev4 /dev/mountpoint" command will mount the given 
mountpoint and open Thunar in that location. When you close the Thunar 
window the filesystem will be unmounted.
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You can use the Alt+F10 keyboard shortcut to stick or unstick a window.
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In the window manager settings dialog, you can select what must be the 
behaviour of the window manager when you double-click on the title bar 
of a window.
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You can use keyboard shortcuts to move a window to another workspace :

Alt + Control + End will move a window to the next workspace
Alt + Control + Home will move a window to the previous workspace
Alt + Control + Keypad-Number will move the current window to 
corresponding workspace
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The Thunar file manager can be driven with the keyboard.
Have a look at Xfce 4 manual to learn more about its commands.
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xfprint4 provides a graphical frontend for printing. It supports either 
CUPS, BSD-LPR or a file as destination, and printers are retrieved from 
the printing system you choosed.

Just configure your printer with the xfprint-manager application, then 
use drag and drop to xfprint4 icon on the panel (or the 'xfprint4 file' 
command) to print.
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Select the "Always on top" option in the Xfce Panel settings dialog if 
your want the panel to always stay above all other windows, and keep its
area uncovered by maximized applications. Selecting this option will 
make the panel use real transparency, if you are running X.org server 
with the xfwm4 compositor enabled.
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Xfce 4 panel offers an autohide feature.
Use it to free some space on your desktop !
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If you want to delete multiple files in the File manager in one step, 
you have to press CTRL while doing right click on the last file. This 
will select the last file and bring up the popup without unselecting 
anything previous. You can also use the Delete key, main menu entry or 
toolbar button to delete all without unselecting.
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You can switch the workspaces by using the mouse
    - and click at the pager
    - use the mouse wheel at the pager or desktop background
    - move the mouse over the workspace edge (if this is activated)
or the keyboard with
    - Alt + Control + Left or Right to step one workspace left or right
    - Control + F<Number> to jump to the workspace
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There are some shortcuts to alter your window size or position:
    - Alt + Control + Shift + Cursor moves the window around
    - Alt + Shift + Cursor alters the size of the window
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xfce4-appfinder is an application finder, which allows you to search, 
launch and find information about applications installed on your system.
You can drag and drop from it to the Xfce desktop menu editor to 
customize your menu.
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There is an "Always on top" option available in the window titlebar 
menu. Select this option if you want a window to always appear above all
 other windows.
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If you click on an entry of the taskbar with the right button of your 
mouse, an action menu similar to the window titlebar menu will appear.
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