Publicaly used Debian box

[Mitja Podreka <mojdebian@gmail.com>]

I'm setting up few computers in a multimedia center wich will be 
available for everybody to use.
I'm using KDE desktop on Debian.
Most of the time the computers will be used to surf on internet, for 
which I want to set up an anonymous account with little rights, but I 
still want the users to be able to use KDE, run other programs, so that 
they can get used of KDE and Linux.
Some of the users will have their own accounts with some hard disk space 
to save their files.

Does anybody have some experiences in setting up this kind of 
environment? As far as I know the normal user cannot compromise the 
system, but is there something that I should take care of? Maybe squtch 
off some program? Hide some file?
Can you recomend some software for monitoring the usage of this computers.

Links would be greatly appreciated.

thanks

Mitja