ReplicatorG - lowering the barrier to 3D printing

ReplicatorG - lowering the barrier to 3D printing
This is the software that will drive your MakerBot Replicator, Thing-O-Matic, CupCake CNC, RepRap machine, or generic CNC machine. You can give it a GCode or STL file to process, and it takes it from there. It's cross platform, easily installed, and is based on the familiar Arduino / Processing environments. ReplicatorG is used by thousands of MakerBot Operators, and has printed tens of thousands of 3D objects and counting.
http://replicat.org/

LinuxCNC (the Enhanced Machine Control)

linuxcnc.org - LinuxCNC (the Enhanced Machine Control) is a software system for computer control of machine tools such as milling machines and lathes.
LinuxCNC is free software with open source code. Current versions of LinuxCNC are entirely licensed under the GNU General Public License and Lesser GNU General Public License (GPL and LGPL)

LinuxCNC provides:

• several graphical user interfaces including one for touch screens
• an interpreter for "G-code" (the RS-274 machine tool programming language)
• a realtime motion planning system with look-ahead
• operation of low-level machine electronics such as sensors and motor drives
• an easy to use "breadboard" layer for quickly creating a unique configuration for your machine
• a software PLC programmable with ladder diagrams
• easy installation with .deb packages or a Live-CD

It does not provide drawing (CAD - Computer Aided Design) or G-code generation from the drawing (CAM - Computer Automated Manufacturing) functions.

• It can simultaneously move up to 9 axes and supports a variety of interfaces.
• The control can operate true servos (analog or PWM) with the feedback loop closed by the LinuxCNC software at the computer, or open loop with "step-servos" or stepper motors.
• Motion control features include: cutter radius and length compensation, path deviation limited to a specified tolerance, lathe threading, synchronized axis motion, adaptive feedrate, operator feed override, and constant velocity control.
• Support for non-Cartesian motion systems is provided via custom kinematics modules. Available architectures include hexapods (Stewart platforms and similar concepts) and systems with rotary joints to provide motion such as PUMA or SCARA robots.
• LinuxCNC runs on Linux using real time extensions. Support currently exists for version 2.4 and 2.6 Linux kernels with real time extensions applied by RT-Linux or RTAI patches.