Here is a great tutorial on how to use a heat gun to recover parts from various boards. You never know when you will need just a small part to finish up a project and you cant find it. Its better to have these parts available when you need them.
You can recycle your obsolete electronic gadgets and learn about how these products are made at the same time. Useful parts to scrounge include surface mount and through hole components, microcontrollers, LCDs, connectors, digital and analog ICs, transistors, LEDs etc
Full tutorial here: Link