While Firefox has an extension for "kiosk" mode and KDE has something similar, they both require some thought and configuration. Opera's implementation seems more robust and simple (although it requires payment and registration). Removing the window manager and keyboard are also excellent suggestions.
The current plan is to set up a Debian box with a journalled filesystem, and as few services starting as possible. Logging into X automatically as a guest user, who has no window manager (probably) and runs only Opera in kiosk mode, reading a local cache of the desired web sites.
I'll write it up for the wiki when it works :-)
-jim
