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Slax, as the name suggests, is based on Slackware, and was originally called Slackware liveCD. It's intended to be used as a liveCD and not installed to your system, much in the style of PuppyLinux, Damn Small Linux, and LinuxConsole, among others.
Where to begin? Using these pocket distros has left me without adjectives to describe how fast they start up, but rest assured, if Slax is not the fastest of all the ones listed above, it is damn close. Power it up, a few line of text scroll by, then you are greeted with a four leaf clover and the name on the splash screen, and immediately into the desktop environment which is KDE.
Slax uses Konqueror as its web browser, JuK as its music player, Kplayer as the default movie player, and features K3b for burning CDs and DVDs.
The Office Suite included is KOffice (KWord, KSpread, KPresenter, and Kontact to manage appointments, addresses and the like) and additional packages can be added by the Slax Module Manager--presumably loaded into ram, though there is the boot option to use persistent changes (i.e., to save to USB or CD session).
Other apps included in the initial modules are KMail, Kopete (Instant Messaging), Akregator (RSS Feeds), and KWifi Manager--to search out those wifi hotspots and configure your wireless card.
Checking out Slax Module Manager a little more fully--it calls itself 'A package management beyond your dreams', but was unable to find any modules to add with the .lzm suffix; undoubtedly a trip Google way could enlighten me--otherwise no clue how to add modules. After taking a quick peek at their website cheatcodes, it is indeed possible to add Flash, though some command line is needed.
Flash video not enabled in Konqueror web browser, though that may be a problem with Konqueror and not Slax itself; apparently the KillBill and popcorn edition include the Flash 9 player, though not this standard edition--and yes, there are three main versions of Slax; the KillBill edition includes Wine and Flash, while the popcorn edition (the smallest) does include Flash as well. There are three other editions (Frodo, Server, and Console) as well.
Streaming (and playing) mp3s does work out of the box, and movies are viewable right away without the addition of any codecs; for pure out of the box enjoyment in a light form-factor (with KDE!), Slax does quite well with the exception of not being able to use or view Flash videos.
Shiny, fast, two out of three ootb (out of the box) requirements (video, music, Flash), all graphical interface (nary a command line needed) with the ability to save work to USB or CD session, a full office suite in KOffice, nice CD/DVD burning software in K3b, all of the most used apps icons neatly laid out in the KDE panel--Konsole (virtual console), web browser, music player, movie player,CD burner, keyboard config tool (switch languages), screen resize/rotate, network config tool, volume; Slax is ready to go almost as soon as you insert your CD (or USB key) for just about anything you could possibly need to do on a computer, even if you have a slow PC with as little as 64M (?!) of ram.
Slax 6.0 stacks up against any of the other pocket distros very favorably, the lack of Flash is points against, but the use of the KDE desktop in a lightweight distro is points given back, and when you consider that this is -rc4 (release candidate 4) and not the final release, before which time they will most certainly fix the Flash issue, and you have a champion pocket distro. At 192M for the standard edition, and 204M for the KillBill edition, you would indeed be remiss in not giving this pocket distro a spin.
Slax is a product of the Czech Republic; their home page is here; download mirrors are here; screenshots here; and Distrowatch info (including reviews by people who know something) here.