As I am now only able to run my machine from liveCD (Fedora XFCE 16 or Xubuntu 11.10), I would like to know if there is a way to keep the current session's settings (keyboard, wifi etc.) for a later session. Can the settings be stored on a USB drive for instance?
You can create a bootable flash drive with the version of Linux you choose, but by nature live cds can't preserves settings. The memory on the disk can't be modified, and the running os in ram can't be preserved. To find out how to create a bootable flash drive, most distros provide instructions. In other words instead of saving the settings on a flash drive, keep the entire os on the usb stick. Make sure that you aren't using the drive as a "live cd" itself, but actually installing the os to the drive. Here's an example http://www.pendrivelinux.com/usb-x-ubuntu-610/ Here's a better link http://www.pendrivelinux.com/universal-usb-installer-easy-as-1-2-3/
Your other option is to find the the configuration files the are used by those individual programs and load them when you start the cd, i.e from usb