I´m building a robot, but I don´t have much money to spend.
So I use the main board of a Sinclair Spectrum from the flea market + some other parts got for free or bought for cent-prices.
I think it´s possible to teach this thing a lot of things,although it´s not high tech.But these old parts are simple and easier to understand than PC parts.
I´m planning to make it a little battle robot, that will be able to eliminate rats with electric power.
For my next robot I got some old AMIGAs and ATARI STs for free, which should certainly be good as mainboards for better robot systems.
So searching flea-markets or looking for things people throw away can be a good idea for moneyless guys like me.