GNU libmicrohttpd is a small C library for embedding HTTP server functionality into other applications. It is reentrant, fast, supports HTTP 1.1, and permits listening on multiple ports. The API is simple and still powerful enough to allow programmers to use the entire HTTP feature set. SSL/TLS support is available as an option.
Frink is a calculating tool and programming language designed to help you in the real world. It tracks units of measurement throughout all calculations and ensures that answers are correct. It converts between systems of measurement, and has a huge library of physical data. It is both a simple calculator for quick calculations and a full-fledged programming language for large tasks. It draws high-quality graphics, handles conversions between time zones, currencies, and historical values of the U.S. dollar and the British pound, translates between several languages, does date/time math, and more.
NanoHttpd is a lightweight HTTP server designed for embedding in other applications. It's only one Java file, in two "flavors", one strictly Java 1.1 compatible, and one at "current" standards. It supports GET, POST, PUT, HEAD and DELETE requests, and supports file uploading with very small memory overhead. Temp file usage and the threading model are easily customized.
Zyan Communication Framework simplifies development of distributed applications. It works on Windows, Linux, Mac OS, and Android platforms via .NET or Mono runtimes. It features LINQ support for three-tier applications, full duplex TCP support, traffic, compression, and encryption, transparent support for events and EBC (event-based components), and Windows and LDAP authentication support.
ReplicaNet is an object oriented C++ library for developers of applications that require a stable and low maintenance middleware solution to networking. Any project that is designed to use a network of machines, such as multiplayer computer games, need to very carefully consider how to approach the design problems associated with networking. It includes support for binary difference patch creation and delivery, backend availability and TitleID verification, Internet CD/license key verification, NAT detection, advertising and querying of sessions, user accounts, friends lists, game invites, chat rooms, persistent data storage, and statistics and ranking.