Well, My name is Ken and I am a mechanical engineering student. I spent a lot of time looking into shapeways.com, but the selection of actual "mechanical grade" material is much greater. Oh, and the color scheme is cooler here too, lol. I am looking forward to populating the mechanical section and hopefully make some money in the process!
I am a mechanical engineer too. I attended Texas A&M University. My undergraduate degree was Manufacturing Engineering actually but I have spent a great deal of my career in mechanical design. You are correct that we have a lot of mechanical materials here and I plan to add more soon.
One of my goals is to bring education to engineering-minded people as well as artists. Engineers are more skeptical about what 3D printing can really do. Let me tell you that we are on the verge of a paradigm shift in the way things are made...it won;t replace mass manufacturing per-se but custom goods are going to get cheaper.
We have a project we are working on right now. I cannot say exactly what but it will be the worlds first 3D printed thing like it in the world and it will shock engineers and everyone that you can actually do this!