Buy a Portable Hard Drive choosing from the major suppliers such as Western Digital, LaCie, FreeCom and Toshiba. For a cheap portable hard drive simply choose the size you want and change the "Sort By" to "Price Low to High".
A portable hard drive is even easier to use than an external hard drive as it requires no extra power supply but gets the power it needs to operate straight from the computer. Some come with dual USB connections, one as a power supply the other for data transfer. Simply plug in to any available USB port (socket) on your computer and away you go!