In the following video, Motley Fool research analyst John Reeves talks about three companies that made major gains this week. He tells us how strong demand in the 3-D printing industry has meant expanded earnings for 3D Systems (NYSE:DDD), how HomeAway (NASDAQ:AWAY.DL), an online marketplace for the vacation rental industry, popped after Barclays raised its rating on the stock, and how General Motors (NYSE:GM) jumped up after announcing this week it would be buying back 200 million shares from the federal government.