DSL (Damn Small Linux) is a Linux distro based on Debian that has been slimmed down to the bare essentials to enable it to run on anything from a 486 up. The great thing about it is that like most Linux distributions it comes with a whole host of hand appliations pre-installed. If you have a network card you have the potential to connect to the internet in a secure and safe environment (connecting to the internet with Windows 95, 98 or ME is not a good idea). This type of slimmed down OS is ideal for countries where access to the latest hardware is beyond the reach of the average person. Take any working machine with a CD drive and you can have a fully loaded system in no time at all.
Another good use for DSL is the ability to have a fully bootable OS on a small USB thumb drive. This can be very handy when diagnosing faults.
Out of interest I took an old Dell Latitude XPi CD M133ST that we had laying around here and work and tried installing DSL on it. I was able to locate this handy how to which helped a lot. Following those instructions closely I was able to install DSL in under 30 minutes. I popped in an old PCMCIA NIC and hey presto I'm on the net. In fact I've been writing this post for that machine, a Pentium 133mhz MMX with 32mb of ram, 1.6GB hard disk and a 12.1" SVGA screen. Obviously it's not the fastest machine in the world but it's more than useable. I could quite easily use email, basic web browsing and IM no problem at all. Add to that the built word processing and spreadsheet apps and I can do all the basics.
I think DSL is well worth a look if you need to ressurect an old machine and want to run on a modern stable OS.