CpuFreqSystemTray is a simple application to monitor and control your Cpu's frequency using cpufreq-utils for KDE. It's really simple to use. Just make sure to execute it within its own directory (it cannot find icons in global paths yet!), or to set it's working directory to it's root path when you create a launcher.
CpuFreqSystemTray needs Python 2.4 (or newer), Qt 4.1.x (or newer),PyQt4 4.1.x (or newer) and Cpufrequtils (the ones which use SysFS).