Puppy Linux has a great feature:
as in wikipedia is mentioned
However, it is possible to save files upon shutdown. This feature allows the user to either save the file to disk (USB, HDD etc.) or even write the file system to the same CD puppy is booted from if "multisession" was used to create the booted CD (on CD-Rs as well as CD-RW) where a CD burner is present.
I would be interested in getting to know if there are any other livecds that also offer this feature?