I used to work for the Free Software Foundation's GNU Project. The Project's goal is to produce the GNU operating system, a complete Unix-like operating system conformant to POSIX.1 and upward compatible with 4.4 BSD. Source code for the whole system will be freely available and copylefted so it stays free.
Here's what I was been doing at the GNU Project:
make; send bug reports to email@example.com.
glibc, Emacs, and many other things from the canonical GNU distribution sites.
Brave souls can get the latest snapshots of the Hurd and C library directly from GNU development machines.