Puppy Linux is a lightweight distro that uses the PetGet and Puppy Package Manger to install and manage software. Puppy Linux is a full Linux system that can be boot from USB, live CD, hard drive, zip drive, network, SD-card, virtual machine, and floppy disk. There are a few official forks/derivatives known as puplets. Some include Racy and Wary. Some unofficial forks also exist. Puppy Linux is perfect for old or slow computers.