Seriously, VectorLinux is a good choice for an old machine - try it if the fat distros feel a bit slow. It is an old and very well established distro based on Patrick Volkerding's Slackware, which is known to be a bit conservative and very stable.
Slackware is a bit of a purists distro and can be somewhat tedious if you are not familiar with Linux and the command line - VectorLinux just makes it easy.
Lean, mean and fast on older hardware (and still looks good)
Mac
