Puppy Linux is a lightweight Linux distribution that focuses on ease of use. The entire system can be run from RAM, allowing the boot medium to be removed after the operating system has started.
Puppy is built with binary packages from the latest Ubuntu release Lucid Lynx, hence Lucid Puppy 5.0. The Puppy architecture is well known to be lean and fast, and friendly and fun, and Lucid Puppy is no exception.
Woof: the "Puppy builder" 
It's a tool that generates a complete Puppy Linux distribution using a set binary packages of the other Linux distribution (Debian, Ubuntu, Arch, Slackware, T2 or Puppy).
It lets developer spend minimal time for maintainership and concentrate on other problems.
To download it follow the instruction here (Firstly you have to install bones).
In 2003 Australian Barry Kauler created the original English version Puppy Linux from scratch. He was the main developer of the first 4 releases, but the last one was almost fully made by community.
Mission and Philosophy
The main goal is to make the most lightweight and still the most usable Linux distribution.
- Small size, ~100MB! This lends itself to some very useful and unique features.
- 'Live' booting from CDs, DVDs, USB flash drives, and other portable media.
- Runs from RAM, making it unusually fast even in old PCs and in netbooks with solid state storage media.
- Very low minimum system requirements.
- Boot time is well under a minute, 30-40 seconds in most systems.
- Includes a wide range of applications: wordprocessors, spreadsheets, internet browsers, games, image editors and many utilities. Extra software in the form of dotpets. There is a GUI Puppy Software Installer included.
- Puppy is easy to use and little technical knowledge is assumed. Most hardware is automatically detected.
The packages for Puppy 4.0 were compiled from source using T2 (http://t2-project.org) back in November 2007. There have been upgraded packages since then, however the original base packages (such as Xorg 7.3) are still being used. In fact, the latest official release, 4.3.1, has been and continues to be our most popular Puppy, and is still "going strong", with many puplets (other puppies based on 4.3.1, such as Puppee, NOP and Lighthouse Pup). Arguably, if this guy works for you, why change? Puppy 4.3.1 release notes: http://puppylinux.com/download/release-4.3.htm The 4.x series is currently undergoing upgrading, with significant improvements. The proposed 4.4 is currently at alpha status: http://puppylinux.org/wikka/Puppy44 .
Barry Kauler, the founder of Puppy Linux and Woof, created Quirky as an avenue to explore the latest ideas. There may be some features in this distro that you won't find in other puppies, either different applications and utilities, different system scripts/behaviour, or even some fundamanetally new underlying behaviour. This is very much a moving target. Quirky is currently built from packages compiled in T2. Some of the ideas may be a bit strange, hence the name "Quirky"! Quirky introduction page: http://bkhome.org/quirky
Wary and Very-Wary
Wary is intended to be state-of-the-art, built with the latest Woof and recent packages, except for some rollbacks where newer packages are considered less than satisfactory. Currently, Wary uses the same T2 packages as Quirky, but Xorg is rolled back to version 7.3 (as, quite frankyly Xorg 7.4 and 7.5 have a lot wrong with them). Wary may be your better choice for older video hardware. Very Wary goes one step further and also rolls back the kernel to version 188.8.131.52 -- again, this may suit older hardware, also we have a large collection of drivers for old analog modems with this kernel -- we are unable to compile many of these drivers with later kernels.
FatDog64 is recently compiled from source using T2 and optimised for the Intel 64-bit x86 (and compatible) CPUs. This built tends to be leading-edge in terms of features and application versions.
Puppeee is a remaster of Puppy 4.3.1, optimised to run on the EeePC netbook. A lot of work has gone into compatibility with EeePC hardware, so this distro is a good choice if you have one of these netbooks. The developer is also planning "Fluppy", which will target a wider range of netbooks.