DGD (Dworkin's Game Driver) is a Modern Mud Server for which I wrote a couple of extensions. They are outdated a bit but given time and the availability of a fully patched release of DGD I will update them again.
Once I programmed a lot in Asymetrix's Toolbook and created some nice libraries like OpenSock, a native wrapper for Winsock that allows Toolbook to emulate Winsock clients but also servers.
Because of the power of Toolbook it's also easy to create applications like web servers serving dynamically created WebPages or VRML models. See the following links: