The plasmoid applicationThis template generates a simple plasma applet with an icon and some text on it.
You need KDE 4.1 to build this template and it uses CMake. You can read more about it on http://techbase.kde.org/index.php?title=Development/Tutorials/Plasma/GettingStarted, all methods are explained here.
Restart plasma to load the applet by issuing kquitapp plasma && plasma or view it with plasmoidviewer YourAppletName.