Puppy linux is what I call it the best of lightweight linux distributions. I have a quite old machine at home, a PIII 500 MHz with 386 MB RAM. While other distros crawl on it (even those which claim to be lightweight), I found Puppy to be rocking on it blazingly fast. It has a technology to load itself to RAM and become quite fast even on old machines. It comes in less than 100 MB and has a wide range of nice applications suitable for older machines. So if you want to breathe life into your old machines, just give it a try. You won’t regret it ;).