IceSL lets you model solid shapes through a simple yet powerful language (based on Lua) and directly
slices even the most complex boolean operations to produce G-code for most printers. It can combine meshes and implicit functions into complex, customizable shapes (in real-time!).
An online version is now available! It does not implement all features but should cover most basic needs. It is in beta and we will continue to develop it further. http://shapeforge.loria.fr/icesl-online/