Progshop.com
The best price shop for programmers, adapter, accessory, zif sockets, eproms and microcontrollers!
http://progshop.com

Tuomo Kortesmaa
Notes and example code for basic operating systems concepts, threads, sockets, and device drivers.
http://users.evtek.fi/~tk/

C++ Sockets Library
A C++ class library wrapping the berkeley sockets C API, and therefore works on most unixes and also win32. Features include, but are not limited to, SSL support, IPv6 support, TCP and UDP sockets, HTTP protocol, and highly customizable error handling. [Open Source, GPL]
http://www.alhem.net/Sockets/

TCP/IP Raw Sockets
MSDN documentation about Raw Socket specification. Raw sockets can be used to create your own protocols.
http://msdn2.microsoft.com/en-us/library/ms740548.aspx

BSD Sockets: A Quick And Dirty Primer
Crash course in programming BSD sockets
http://www.ugu.com/sui/ugu/show?I=help.doc.network.sockets&F=1111111111&G=Y

Tooltronics, Inc.
TOOLTRONICS Inc. specializes in high current Kelvin test sockets, burn-in sockets and test fixtures, focusing on but not limited to the DC-DC/Power Converter market. The company has a strong 44 year track record.
http://tooltronicsinc.com/

Excel Cell Electronic
Manufacturer of DIP switches, terminal blocks and sockets, solid state, electromechanical and photo mos relays, and zif sockets and modular plugs.
http://www.ece-usa.com/

Simple Sockets Library
Sockets library for UNIX platforms that looks much like regular C-style i/o. [Open Source, Free]
http://mysite.verizon.net/astronaut/ssl/

An Introduction to Sockets in C Through Annotated Examples
An introduction by example about sockets with the C programming language.
http://www.math.grinnell.edu/~walker/c/sockets-index.html

Netzwerkprogrammierung mit Sockets und C
Einführung in die Netzwerkprogrammierung mit Hilfe von Sockets (Client- und Serverprogrammierung).
http://www.uvomatik.de/programmierung/