If you are interested in getting that really old machine up and running again, with as little as ~32MB of ram, then there is a shiny new competitor to PuppyLinux and Damn Small Linux: TinyMe.
I know that Ubuntu is all the rage now, but I have had some serious issues with getting wireless working on my Thinkpad (Intel 3945 a/b/g) when using the roaming feature (e.g., at coffee shops, airports, etc.) and so have been using PCLinuxOS for the past couple of months; the fact that it allows you to use the 'productivity' of Beryl (think 3D spinning cube, Mac-like Expose feature) is only a plus.
When I heard that TinyMe was released by the same group of folks who put out PCLinuxOS, I was naturally intrigued, having a really old Compaq (7 years old) lying around gathering dust.
TinyMe is a natural fit for such machines, and the speed and ease of installation, as well as the ease of use once it is setup are both huge pluses in its favor.
While I had been using DreamLinux on the old laptop without any complaint, I decided to set up something much more lightweight as a buddy is going to the far, far east, and needed some extra hardware for the people he is going to be teaching there. Think one laptop per (100) child(ren). As they are short of just about everything there (think yurts), I wanted to install something that would leave as much room for all the reading material and other educational stuff he could pack on there, all with the minimum of overhead in ram usage while leaving tons of hard drive space.
TinyMe uses the OpenBox window manager, and comes with just the bare bones for everything you need to do on the web or otherwise; instead of Firefox it features the lightweight Opera browser, in place of Open Office writer there is Abiword and medit--full details of all it contains can be found at this mini-review here.
As with PCLinuxOS and Mandriva, TinyMe uses the Draklive installer, and they just don't come easier than this; eight minutes from clicking the install button until I was rebooting into the slick blue desktop and surfing the web.
You will need to connect to the repositories to install Flash and mp3 and DVD playing software; the nice thing about this is that they are already in the fully configured repository (the same one used by PCLinuxOS and a separate one for TinyMe), so no depending on Automatix a la Ubuntu, or Livna repositories for Fedora. Not a huge task, but nice that it comes set up for upgrade from the get go.
TinyMe takes up around 700MB of hard drive space, and the download is only a 180MB ISO file; burning the ISO file to disk was the matter of a moment. As I had recently replaced the old 20GB hard drive with a newer 120GB one, I figured that my friend could likely fit most of the Library of Congress (and perhaps Wikipedia as well) while still having room for some pirated Britney Spears CDs easy listening and a few video clips.
Though there are smaller Linux distributions out there, such as DSLinux, PuppyLinux, and NimbleX (KDE in less than 100MB), none were as nice looking or swift, at least on this machine. Boot time is freakin' unreal--we're talking in seconds, not minutes, and logout, reboot, and shutdown are also scarily fast. Yeah, it's Linux, so not much rebooting necessary, but if you are going to be in a place where the electricity is not always that reliable, a bit of a factor nonetheless.
Automatic disk partition, fast install, easy to set up, upgrade and fast on older machines with slower CPUs and limited ram, speedy boot speeds and pretty as well--what's not to like? Well worth the download, and if you aren't impressed in the liveCD, you can just take it out and you are back to your original system. Oh, and if you don't want to install it to your system, you can always install it to a USB flash drive. Pretty nifty.
They don't come any friendlier than this, and even if you are just first hearing about Linux now, there's literally nothing to this learning curve--download ISO, burn to disk, insert disk, click install, input info, and reboot, and Bob's your uncle. No better time to put that old machine to use, and have some fun in the process.
As always, if you have any tech-related stuff, comments, questions, etc. not directly related to the above, please feel free to chip in. Cheers!