If you wish to print in well established materials then Shapeways website is fast and efficient. Want to print in one of their newer materials? Good luck!
You first have to register' for the material you want. You can't place an order in the normal way (they don't tell you this), instead you must engage in correspondence with an administrator who, seemingly, is unaware you can't place an order through their website. I've failed so far to get an order placed and i'm ready to give up!