www.Shapeshift.io is a great site where you can change on coin to another coin without even registering. I've used it in the past and it works really well.
However at the moment stellar lumens isn't an option to trade, it would be great if they were on it to gain more traction for stellar. How about we get in touch with them using their contact form https://shapeshift.zendesk.com/hc/en-us/requests/new and see what happens? If enough people ask I'm sure they will add Stellar!
