SliTaz is awesome. I've used it in the past during its 3.0 days, and since then I already found it fascinating. If you haven't heard of it, here's a short description of the distribution, provided by their website:
SliTaz GNU/Linux is a free operating system working completely in memory from removeable media such as a cdrom or USB key. It is light, speedy and fully installable on a hard drive
Sounds familiar? That's because Slitaz belongs to the minimalist family of Linux distros, which Puppy Linux and Damn Small Linux are part of. Slitaz is a tiny ISO (~30MB) and loads into RAM on boot, making the Live session about as fast as a hard drive install. Although other distros could do the same, usually they're too big to fit completely. Slitaz, on the other hand, is small enough to fit even in 128MB of memory, making it the right match for that old computer sitting in the basement.
Slitaz 4.0 was released on April 10th, and I promptly downloaded it. Finding that no one (at least in Distrowatch) ever reviewed it, I thought I'd show my appreciation for this distribution and do it: