Sam Leffler did a lot of contributions to the networking code in
BSD. Specifically, he's the one who figured out how the socket
interface was really supposed to work for iterative servers, so
that the accept(2) system call returns a new socket every time
it returns with a client connection. His design made it possible
to write numerous TCP servers as we know today, including telnetd,
ftpd, and httpd.
Sam later left CSRG and moved to Lucasfilm and then Pixar,
where he developed RenderMan,
a phenomenal distributed/parallel graphics rendering software used
in a number of productions, including the first feature-length
computer generated animation movie, Toy Story.
He then worked for a while at SGI as a researcher, where he developed
libtiff, a widely used free library to manipulate TIFF images
on Unix. Sam also developed FlexFax, later renamed to HylaFax,
a package for sending fax on Unix. If you want to read well-written
C++ source code (which is hard to find), HylaFax is for you!
He later moved to VMWare, and finally started an independent
business with some other folks, errno.com.
Sam's home page
which probably is not very up to date, but gives you an idea as to
what he has done...