Plan 9 from User Space moved from http://swtch.com/plan9port here. See also the Google discussion group https://groups.google.com/forum/#!topic/plan9port-dev/OqSvUDfwS-M.

Baudline is a time-frequency browser designed for scientific visualization of the spectral domain.  Signal analysis is performed by Fourier, correlation, and raster transforms that create colorful spectrograms with vibrant detail.  Conduct test and measurement experiments with the built in function generator, or play back audio files with a multitude of effects and filters.  The baudline signal analyzer combines fast digital signal processing, versatile high speed displays, and continuous capture tools for hunting down and studying elusive signal characteristics.

Code can be found on https://github.com/froggey/Mezzano
Documentation is sparse, but it appears to target x86.

Executable Wiki: non-linear, text-based shell. I am not explaining this well, take a look at the screencasts.

Despite the availability of many excellent books and scientific articles and daily discussions on comp.lang.fortran, information about modern Fortran programming is sometimes difficult to find. There is a need for something that changes faster than books, papers, and documentation, but is more persistent and organized than a newsgroup. The Fortran Wiki aims to fill this void. Its mission is to provide an open and community-driven venue for documenting and discussing all aspects of the Fortran language, from compilers and standards and best practices and design patterns.

V3 SNOWLeo SDR is a low-cost open source software defined radio platform based on Xilinx ZYNQ SoC and MYRIAD RF module. It include Giga Ethernet, USB OTG, HDMI, SDIO and USB-UART. SNOWLeo SDR is equipped an MYRIAD module that support 300MHz~3.8GHz, 28MHz BW application, such as WiFi, LTE or WiMax.

Radare project started as a forensics tool, an scriptable commandline hexadecimal editor able to open disk files, but later support for analyzing binaries, disassembling code, debugging programs, attaching to remote gdb servers, ..

The Purely Functional Package Manager

Nix is a powerful package manager for Linux and other Unix (including OS X) systems that makes package management reliable and reproducible. It provides atomic upgrades and rollbacks, side-by-side installation of multiple versions of a package, multi-user package management and easy setup of build environments.

Lots of information about amateur radio, software defined radio. From the author of linrad, a software receiver for Linux (which also runs under Windows and OS X).

The firmware for airspy will be released once it is cleaned up.