Under KDE at least, control-c for copy and control-v for paste work pretty much everywhere (perhaps because of klipper?) even if right-clicking doesn't give you the options.
The equivalent of taskmanager for killing processes that won't die is "KDE System Guard" under the KDE menu and System. (Yes, things still stop working.)
If you don't get sound in KDE, the first thing to check is the volume so run Kmix and check the PCM value and Master volume (and for me, the VIA DXS stuff too).
The text editor Kate rocks. It is especially good for giving access to a shell ('terminal' at the bottom) for extra power/control.
Make full use of the virtual desktops (set different wallpaper for each!) for extra organized-ness. You can make it so that each desktop only lists the programs for that particular desktop in the bar (right-click on KDE bar to get customization options).
Hold Alt and you can (left-) drag whole windows. Holding Alt also lets you resize windows by right-dragging.
If you use gnome, too bad cos I didn't even bother to install that .. ;)