Have used emachineshop.com in the past so used to their CAD and assuming that this site has one too..... but I can't find it.
I can find template bits but I have something specific to design. I could, I guess, go & get a CAD prog & upload the file in a suitable format but you must have one here somewhere that'll save me going to those lengths?
There is a VERY basic editor at http://tinkercad.com/ or under the create menu, labs option. However now that Shapeways supports DAE files, Google Sketchup 8 is a good free alternative. There are other more comprehensive options as well if you want something more involved.