Autodesk free software for Students - http://students.autodesk.com/ 


[Opensource/Free Architectural Solutions]


Operating systems: 
Linux based systems 
Ubuntu 
Fedora 
openSUSE 

Office Applications
Open Office
LibreOffice
IBM Lotus Symphony
Google docs


2D Drafting Applications:

DraftSight

3D Modelling, Rendering Applications:

Sketchup
Blender
Kerkythea  -Renderer
Brazil Rio   -Renderer 

Image editing and manipulating:

Gimp
Paint.NET
Photoscape

Desktop Publication
Inkscape
Scribus

Movie editing and manipulating:

AVS Video Editor

Virtual Reality Simulation/Game engine

http://openwonderland.org/

Unity 3d


Augmented Reality Software

BuildAR

Metaio Creator


3D Printing

Meshmixer

Sketchup STL plugin