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.

Interesting articles about amateur satellites.

Project to create a mobile phone with open hard- and software.

This dsPIC-based project receives and decodes the pseudo-random phase-modulated signal from the DCF77 time code transmission to achieve sub-millisecond timing accuracy. It is the the subject of an article in the Jan 2012 edition of Elektor magazine.

ChibiOS/RT is a complete, portable, open source, compact and extremely fast RTOS (Real-Time Operating System). You may start reading this introduction.

The sigrok project aims at creating a portable, cross-platform, Free/Libre/Open-Source signal analysis software suite that supports various device types (e.g. logic analyzers, oscilloscopes, and many more).

It is licensed under the terms of the GNU GPL, version 3 or later.

Geiger counter kit, can measure alpha, beta and gamma radiation, includes GPS receiver. Open source hardware.

Convergence is a secure replacement for the Certificate Authority System. Rather than employing a traditionally hard-coded list of immutable CAs, Convergence allows you to configure a dynamic set of Notaries which use network perspective to validate your communication.

xv6 loosely follows the structure and style of v6, but is implemented for a modern x86-based multiprocessor using ANSI C.

ACKNOWLEDGMENTS
xv6 is inspired by John Lions's Commentary on UNIX 6th Edition (Peer
to Peer Communications; ISBN: 1-57398-013-7; 1st edition (June 14,
2000)). See also http://pdos.csail.mit.edu/6.828/2007/v6.html, which
provides pointers to on-line resources for v6.

MIT license.

How to cross-compile Go programs.