i have always had an old gateway upstairs that i gave up hope on when the cpu fan broke, but recently i have been positively bombarded with old hardware to play with:
i have: 3 old (beige, running win 98 or 95 i cant remember) satellite laptops
one newer vaio netbook that is running ubuntu 10
one very old compaq that doesnt have a functioning hard disk
my current ubuntu/vista/lucid puppy superlaptop

i was thinking of playing with a single system image sort of thing, but i dont seem to be able to find the right software.

all the computers have a cd drive except the ancient compaq that has a floppy

so: any suggestions on what to do with it all? i am interested in ideas like load balancing,

For older machines you should have a look at kmandla's blog, he always have some interesting ideas for them.

Check this site out: http://freelinuxbox.org/

You may be able to spread the Linux love that way.

Cheers

Perhaps http://www.freecycle.org/ might be of interest as well

A very simple way to run knoppix on all systems is to boot one system and start knoppix terminal services. Follow the prompts and in a few minutes you will be able to net boot them to knoppix. If all don't support pxe one can make a gpxe floppy,cd, or usb to boot it.
Once the knoppix is set up you can see how it was done and can change images to suit or setup another deal.

If you want you could also look at 2x's stuff.

Gpxe to internet may also be an idea. See netboot.me or boot-kernel.org