Put a cable tie (that has an added eyelet) around the power cord and then affix a hook to a nearby surface and hang the cable from it. You can also double them up and attach them to a chassis screw or around the feet of your amp and other component
http://www.cabletiesplus.com/Products/5-Mounted-Head-Cable-Ties-(40-lb)-(Natural)__CP-5-40MH-N.aspx
http://www.cabletiesplus.com/Products/5-Mounted-Head-Cable-Ties-(40-lb)-(Natural)__CP-5-40MH-N.aspx