Tatlin is a python-based Gcode and STL viewer. You can either download the project in a .zip or .tar, or clone it from git.
The project requires a few python related packages to run (as documented on the project website). On a Xubuntu 13.10 system, the following commands should be sufficient:
sudo apt-get install python-numpy python-opengl python-gtk2 python-gtkglext1