All software bellow either knows how to interface with, or how to generate g-code for, Smoothieware.

3D Printing

• Slic3r - 3D printing slicer
• Cura - 3D printing slicer and host.
• Pronterface - 3D printing host. See the guide on the Wiki : Pronterface
• 3Delta Printer Control - 3D printing host especially suited for delta printers.
• OctoPrint - Awesome web interface for 3D printer control. On the wiki : Octoprint
• Simplify3D - Closed source 3D printing slicer and host. On the wiki : Simplify3D Requires post-processing of gcode to use on smoothie, see http://mikk36.eu/SimplifyS3D/

CNC

• bCNC - Open-Source CNC host with great preview and other operations. Set machine type to smoothie. and add grbl_mode true to your smoothie config.
• OpenSCAM.org - Open-Source Simulation & Computer Aided Machining (Free 3-axis CNC Simulator which understands G-Code)
• OpenSCAD.org - Open-Source CAD software.
• GCode plug-in for InkScape - Output GCode from SVG files in Inkscape.
• PyCAM - Open-Source CAM software.
• More links at ShapeOko.com.
• jscut - Open-Source in-browser CAM software.
• CamBam - Closed-Source, but cheap and feature-full CAM software. Widely used by hobbyists.
• Fusion360 - Closed-source, free for hobby/fablab/small business.

Laser

• GCode plug-in for InkScape - Output GCode from SVG files in Inkscape. Video tutorial.
• Visicut - Full laser control application, has Smoothieware interface. Video tutorial.
• LaserWeb - Web-based full laser control application, has Smoothieware interface