quick changing of configs in Cisco devices

I have a small network of Cisco devices, routers, switches, PIX etc.

I want to use it in a test lab, have people try out dif’t configs,
equipment then at the end of the day, purge all the configs and go
back to a known config. How does one do this, software or
freeware? I would ultimately want a hardware “switch” that I can
flip to delete all the test configs and go back to a known state.

Thanks