A list (Alphabetical) of software, I have used, for teaching, and others!
Calculix, FEA Program, Free and very versatile: http://www.calculix.de/
CBA, Software for shear force and bending moment diagrams of continuous beams: http://sourceforge.net/projects/cbeam/
Ftool, A structural analysis educational interactive tool: http://www.tecgraf.puc-rio.br/ftool/ftooleng.html
Frame3dd, Structural Analysis program, Static, Dynamic for 2D and 3D frames and trusses: http://frame3dd.sourceforge.net/
Freemind, mindmapping: http://freemind.sourceforge.net/wiki/index.php/Main_Page
GNOME: My desktop: (I use the classic desktop) http://www.gnome.org/ (moved out as of now)
GNUPlot: Basic Plotting program: http://www.gnuplot.info/
GNU Octave: For plotting and other mathematical computations: https://www.gnu.org/software/octave/
Matplotlib: For plotting data anything to everything: http://matplotlib.org/
Mendeley, Research made easy: http://www.mendeley.com/
OpenSees Parallel FEA Analysis specifically designed for Earthquake Analysis: http://opensees.berkeley.edu/
Phatch, Batch Processing of Photos: http://photobatch.stani.be/
Scilab, Replacement for Matlab: http://www.scilab.org/
Shotwell, Photo Library: http://www.yorba.org/projects/shotwell/
wxMaxima, Algebra! : http://andrejv.github.io/wxmaxima/