J-Doc

Change Gnome panel font color

To change the colour of the fast user switching applet, open the file to edit the colours with:
$ gedit .gtkrc-2.0
Then add these lines into the file (#FFFFFF for white):
style "modpanel" {
fg[NORMAL] = "#FFFFFF"
}
widget "*PanelWidget*" style "modpanel"
widget "*PanelApplet*" style "modpanel"
widget "*fast-user-switch-applet*" style "modpanel"
Now run this code to reload the panels:
$ killall gnome-panel
(Taken from http://ubuntuforums.org/showpost.php?p=4315463&postcount=10)

Change desktop folder in Gnome

You need to edit the file ~/.config/user-dirs.dirs:
$ nano ~/.config/user-dirs.dirs
Modify the XDG_DESKTOP_DIR entry as needed. For instance:
XDG_DESKTOP_DIR="$HOME/.desktop"

Make Audacity work with Pulseaudio

Rename the file /usr/bin/audacity to /usr/bin/audacity.original:
$ sudo mv /usr/bin/audacity /usr/bin/audacity.original
Create a new /usr/bin/audacity file using:
$ sudo gedit /usr/bin/audacity
Then write the following lines into the file:

#!/bin/bash

padsp audacity.original "$@"

Save the file and make it executable:
$ sudo chmod +x /usr/bin/audacity
Enjoy! You can use the same trick with Skype and avidemux

Make Thunderbird the preferred email application for KDE

Modify the file $ ~/.kde/share/config/emaildefaults so it looks like this:

[Defaults]
Profile=Default

[PROFILE_Default]
EmailAddress=
EmailClient[$e]=thunderbird
FullName=First Last
Organization=
ReplyAddr=
ServerType=
TerminalClient=false

Change Icon Size in Konqueror

Under the [Settings] section in $ ~/.kde/share/config/konqiconviewrc modify the following parameter:
IconSize=48

Turn off the PC Speaker (Bell)

Uncomment the following line on /etc/inputrc:
set bell-style visible
and restart.

Custom Icons

A complete tutorial is available here.