I really love working with many different operating systems. Some of them I use for daily work and some others I am just playing with to see, how they work. Perhaps I will try to introduce some of them here from time to time.
One of my absolutely favorite Linux systems is Puppy Linux. You can get several different flavors of it, I use Bionic Beaver, coming from Ubuntu. One word first: Puppy Linux is no fork of any Linux distro. The devs take the best of several systems together and build a completely new distro - Puppy Linux.
Take a look at their website.
I chose Bionic Beaver and worked before with Xenial Pup. Here is a screenshot from Bionic Beaver:
How does it work?
Fast. Incredible fast. Puppy Linux is a live-os and you can run it from every CD/DVD/USB-Stick, whatever you like. You can even install it (frugal install) to the harddrive. Further you can set an encrypted partition for your own data. Every saved settings or data is provided there and nobody can visit them. It is a LUKS encryption, as used in many Linux distros.
After booting the whole system is build into the RAM, what makes it absolutely fast, even on old machines. No other system can be faster on your machine. I use it on my old eeePC with 2 GB RAM and it works fantastic.
You can just shut down your system, put off the USB-Stick with Puppy Linux and use it at the next machine. Where ever you like it to use.
What's in it?
Puppy Linux comes with many, many software for nearly every purpose. Most of the default apps are lightweight (of course), but very useful. The devs made a very good job here. With the packet manager you can install much more software. But again, it is not Ubuntu.
$ apt-get does not work. But you will not miss a thing.
Bigger packets like LibreOffice can be loaded on the fly with an *.sfs file. It is similar to an app image. You can download it, load it and work with it. If you don't need it anymore, you can unload it to save RAM space.
Browsers, Chat, Mail, Text-Editor, Spreadsheet-Editor, PGP, Picture Viewer and Editor, everything is on board.
Where is the catch?
There is no. One may say, you only work with a single user, root. That is right. But consider, everything is running in the RAM. Reboot your machine and everything is fresh and new. It is a good system to even do online-banking. When the system is loaded, you can put off your USB-Stick and just work on. Nothing can happen to your stick.
Puppy Linux has a big active and friendly community. Go to the website and join the forums. There is a #puppylinux channel on Freenode IRC.
I recommended to give it a try and I appreciate you will use it. Really.