Originally Posted by Antipode

If your hotel won't do it for you or if you have trouble getting in contact with them, I used www.ticket-machupicchu.com/ and it worked for me. The markup is a little higher than 10% ($61 for the regular entry ticket), but it was better than a few travel agents I tried to contact. They got back to me in about 2 business days with a ticket that I can print out.