The entire desire to do this came about from reading about building a Stratum 1 clock using a Raspberry PI at http://www.satsignal.eu/ntp/Raspberry-Pi-NTP.html and from the use of a Sony radio clock to provide WWVB pulses from the WWVB receiver module that was used in the radio clock.

However, all of the projects and examples I found used Linux which I did not really want to use. I much preferred to use NetBSD, but it lacked a number of critical features that would be required to make a properly working Stratum 1 clock. Interrupt support for the GPIO pins was needed and adding a PPSAPI driver that could be triggered by a GPIO interrupt would be necessary.

This is an all new two volume text, completely revised Jan 2011,
text covers how the GPS works from basics all the way through the
operation and implementation of the GPS100SC receiver, a custom
single channel receiver. The text is unique in that not only is
theory covered but the complete details of a functional design
are presented. Detailed schematics (down to part level) and all
design CAD files are included. In addition a chapter is devoted
to the Zarlink chip set, an open software source receiver and all
new material on the Turbo Rogue receiver designed by JPL. There
is no other text like this text. If you want to know how gps
works and how a receiver can be implemented this book is for you.

Wiki about satellite navigation, developed under an ESA contract.

Another GNSS software receiver, written in C++ and licensed under GPL 3.0.

L1/L5 coherently sampled TRIGR data files containing the L5 test transmission from SVN49.

SaVi - satellite constellation visualization. Simulate Iridium, Globalstar, Sirius, GPS, Teledesic and other systems, modify them, or design your own. Uses Tcl/Tk and Unix libraries; 3D viewing option requires Geomview running on X Window. BSD license.

OpenSource GPS is software for x86 PCs that allows you to acquire, track and demodulate signals from GPS satellites. OSGPS requires a Zarlink GP2021 12 channel GPS correlator chip or software receiver hardware such as the GPS1A, see www.gpscreations.com. Does not appear to be very active recently.

Nice rant on the advantages of plain text e-mail. Has some software for GPS navigation as well.

More information about the Holux M-241 GPS logger.

Just what it says, with emphasis on OS X.