I always carry a debian-live system in my keyring, it is an image (built by myself using a git repository) that I installed in a USB pendrive.
The device has three partitions. The first one contains the debian-live system itself, the second one is used for persistence and the third one is an extra fat16-formatted partition to copy and move files around easily. Here is the layout:
It is really handy to to be able to carry your operating system with you everywhere you go. You can boot it on almost any machine you have access to, saving your data in the pendrive. It is also a great tool to test hardware before performing an installation (the image includes an installer).