Thorny topic of editing the menus, removing some items or adding some site-specific items.

Get rid of workspaces as much as possible - lockdown to only one workspace, remove the pager from the panel, kill the shortcuts keys for switching workspaces.

Disable access to the terminal - set the disable_command_line key, remove the "Open Terminal" thing from the desktop background menu, disable the mini-commander applet, disable console switching with the /etc/inittab hack.

Disable log-out, including Ctrl-Alt-Backspace.

Internet cafe kiosk-mode thing with only a full screen browser?

Set the proxy and lock it down? Probably have to make epiphany the default browser as well for it to be meaningful.

Disable the screensaver, disable selected screensavers, disable lock screen etc.

Add desktop icons to the default desktop.

Disable nautilus altogether?

Printers - setting things up to point at a sane set of printers by default?

Branding the desktop - rhgb, gdm, splash screen, menu icon, desktop background, default home page for the browser...

Change default mime-type handlers.

Disabling turning the computer off? Possible?

Deploying these changes in a sane manner - packaging stuff up in RPMs, doing stuff in kickstart etc.