A large quantity of published data is available only in the form of plots and it is often difficult to extract numerical data accurately out of these pictures. There are several softwares available to aid this process, but most are either paid, difficult to use or lack some essential features. Also, many of the existing programs work only on a few specific operating systems and require installation by the user. Most programs only support 2D X-Y plots and so it is not possible to work with polar diagrams, ternary diagrams, microscope images or maps. With these issues in mind, WebPlotDigitizer was developed to be an easy to use, free of charge and opensource program that can work with a variety of plot types and images. This program is developed using HTML5 which allows it to run within a web browser and requires no installation on to the user's hard drive.
Distributed under the GNU General Public License Version 3.

Found on John D. Cook's blog
http://www.johndcook.com/blog/2016/04/20/how-to-digitize-a-graph/

Changed URL from http://arohatgi.info/WebPlotDigitizer/ 2019-12-30

A compact Raspian based distribution
for the Raspberry Pi board computer.

On-line dictionary (german<->english, but other languagues are supported).

Gpredict is a real-time satellite tracking and orbit prediction application. It can track an unlimited number of satellites and display their position and other data in lists, tables, maps, and polar plots (radar view). Gpredict can also predict the time of future passes for a satellite, and provide you with detailed information about each pass.

The RADclock project (formerly known under 'TSCclock') aims to provide a new system for network timing within two years. We are developing replacements for NTP clients and servers based on new principles, in particular the need to distinguish between difference clocks and absolute clocks. The term RADclock, 'Robust Absolute and Difference Clock', stems from this. The RADclock difference clock, for example, can measure RTTs to under a microsecond, even if connectively to the time server is lost for over a week!
The RADclock is available and can be used as an alternative to the ntpd daemon to provide convenient system clock synchronisation for systems running FreeBSD and Linux. In terms of local hardware, it exploits the availability of counters such as the HPET counter or the TSC (Time-Stamp-Counter) commonly found in PC architectures.

Circuit simulator with Qt-based GUI.
The Qucs GUI is well advanced and allows setting up schematics and presenting simulation results in various types of diagrams. DC, AC, S-parameter, noise and transient analysis is possible, mathematical equations and use of a subcircuit hierarchy (with parameterised subcircuits) are available. Qucs can also import existing SPICE models for use in your simulations.

Simple function plotter with (currently not foolproof) zero (or intersection) finder.

gmeteor is a tool for designing discrete-time equiripple filters with linear phase and a finite impulse response (FIR). With gmeteor, you can design filters with an arbitrary frequency response. `gmeteor' runs on systems that support the Guile extension language from the GNU project (for example, GNU systems running on a Linux kernel). `gmeteor' is free software distributed under the terms of the GNU General Public License (GPL).

Interesting window manager (for X11), extensible via Lua.

Blog written by Juan Jose Garcia Ripoll, maintainer of the Common Lisp implementation ECL.