The following links provide direct links to the Windows Dynamic Link Library (DLL) tutorial with code examples available at Tenouk.com and its' friends:
Win32, C and Dynamic Link Library (ANSI) - The Win32 and C programming for DLL
Win32, C and Dynamic Link Library (Unicode) - The Win32 and C programming for DLL using Unicode
C++, MFC and Dynamic Link Library - C++ and DLL programming for Microsoft Foundation Classes
The C++ .NET, Assembly and Dynamic Link Library - From DLL to the Windows Assemblies
Search www.winsocketdotnetworkprogramming for C#, VB .NET and C++/CLI DLL.