These tools will guide in you designing and printing your 3d designs. All are free.
gCode and printing preparation
ReplicatorG – converts STL files to gcode and gets them ready for printing
Netfabb basic – useful for splitting STLs into multiple components
Makerware – Makerbot’s proprietary gcode conversion tool
gcode visualizers
http://gcode.joewalnes.com/sample files
Maker Faire Robot – download the file named MAKE_Robot_V6.stl – it’s the last one on the list.
AWHS Computer Graphics 