libmls is a library that can be used to measure the frequency response of a loudspeaker or a room using your computer and an ordinary soundcard. It can perform both MLS (Maximum Length Sequence) and Sinus sweep measurements. It supports ALSA, OSS, and the sound system used in Windows.
nMicrocoder is an ncurses EDA tool to write microcode. Basically, it is a stripped down spreadsheet program that lets you fill a table with "0", "1", and "-", and gives you compile-ready verilog code in return. It was written as an alternative to full spreadsheet programs. It is known to run on Linux, IRIX, and Solaris, unless ncurses 5.3 is installed.
Ngspice is a mixed-level/mixed-signal circuit simulator based on three open source software packages: Spice3f5, Cider1b1, and Xspice. Spice3 is the most famous and widely used circuit simulator. Cider is mixed-level simulator that includes Spice3f5 and adds DSIM, a device simulator. Cider couples the circuit level simulator to the device simulator to provide greater simulation accuracy (at the expense of greater simulation time). Xspice is an extension to Spice3 that provides code modeling support and simulation of digital components through an embedded event driven algorithm.
pdnmesh is an automatic, 2D Delaunay mesh generator, and a solver for finite element analysis. It is capable of producing PostScript output of the mesh and contours. It is possible to use DXF files as input after filtering. It requires GTK/GtkGLExt and Mesa/OpenGL or MFC (Win32), and is written in C.