OS Family: Linux
Developer: Tomas Matejicek
This is the best tiny distribution I've ever found for new Linux users; it's easy to use with a potent desktop environment (KDE 3.5) and with Linux kernel 2.6 that offers a good support of different hardware (USB, wifi…etc).
Based on the Slackware distribution, Slax is can be run from a small minidisk (or even from a bootable USB); its standard version has nearly a 190 MB size, this let me make a copy of it I always have in my pocket when I go to university :)
Slax does not pretend so much in matter of requirements, to run the Xwindow window manager (with KDE) you will need 144 MB of RAM memory, your processor will be good for sure (minimal i486 Pentium or AMD needed).
Slax comes in different editions: Standard, KillBill (that I have), Server and Popcorn. KillBill contains qemu and wine, Popcorn is only 128 MB (good if your flash is of this size).
Another characteristic of Slax is its modularity, modules for Slax can be easily added and you can find thousands of them on the web.
Official Site of Slax is here