Several big companies donate their computers, hardware to charities for many reasons to do good for society or to get tax exemption and many other good reasons. The basic thing is people or organizations which can not afford the computer can operate and can make their career. Your helping hands to such organizations can make a difference as Information Technology has changed a lot of stuff of life in past decades and will continue to change.
These refurbished free or low cost computers can be easily adopted for educational purposes as their hardware need is not too much. And biggest advantage to such programs are less electronic waste, less pollution. Think of it, Support it.
Here is a good list of organizations involved in such programs for UK. http://www.itforcharities.co.uk/pcs.htm , you can contact nearby organization to join any good program.
Charity is always good.