This project is kind of mad, but the results could be pretty useful. Instructables user catwood guides you through the process of building a wood lathe from mostly discarded parts. Along the way you will need things like the motor from a washing machine and the frame from a bike. It might make sense to buy or construct a more sturdy piece of equipment if you plan to make wood turning a full time hobby, but for light duty projects I could definitely see this coming in hand.
Want a lathe? Make one from junk