A browser based 3D CAD program that runs in the browser.It is very reminiscent of OpenSCAD ManifoldCAD Those of you who are comfortable with Javascript might find this appealing. Objects can be exported as GBL which can be opened in CURA
Category: 3D Printing
Free Online STL Repair tool
With this tool you get your STL file checked for errors. It also automatically proides a fixed downloadable version.
Thingiverse
Ultimaker have taken over this 3D modelling resource, which was originally founded by MakerBot.