I completely agree, don't think that newer linux distro's can't run on older hardware, infact they can run just as fast as the older ones. Its only bloated ones like Fedora which come with stuff like Gnome, KDE, and a lot of excess bloat which makes it slow.
My personal recommendation is Vector Linux 4.3, its a fast and easy to use distro, and you wont have problems of packages as it can use slackware 10 packages quite well -
www.vectorlinux.com
Then, you can try slackware or gentoo, both are very fast, though it may take a little patience to get them running at first, its well worth the effort.
The important choice for you is the window manager. Don't go for a bloated Desktop Environment like KDE or Gnome, just stick to a simple Window Manager. I recommend IceWM, it runs fast as hell and has many powerful features. Also you can use fast software like Opera (browser), X Win Commander (File manager), mplayer (media player), Sylpheed-claws (mail client) etc.
Check *users.netwit.net.au/~pursang/lofat.html
