KDE Kiosk Admin Tool
LinuxLibrarian.org has an article about how to install and configure KDE Kiosk Admin Tool. The Kiosk Admin Tool is a great feature that lets you easily limit access to only some computer functions. More details about the KDE Kiosk Admin Tool can be found on Linux.sys-con.com, including an interview with the creator of the tool.
If you are not technically-minded and don't want to build the software from source code, you can use a Linux distro like Kubuntu, a KDE version of Ubuntu, to install the KDE Kiosk Admin Tool with just a few click in Synaptic Package Manager. You can find Synaptic in the menu by going to System —> Administration —> Synaptic Package Manager.
This is the Synaptic Package Manager screen on Ubuntu. You should be able to install KDE Kiosk Admin Tool on Ubuntu like this. You should also download KDE with Synaptic and on your next login choose the KDE desktop instead of GNOME. Using KDE on Ubuntu basically turns Ubuntu into Kubuntu. If you are already using Kubuntu, Synaptic will look similar to the image below and you will already be in KDE when you login.