the XML C parser and toolkit developed for the Gnome project (but usable outside of the platform). Code is portable (to Linux, Unix, Windows, embedded systems, etc.) and modular; most of the extensions can be compiled out
MSLU comes with licensing terms that are highly unfriendly to Open Source applications: although you can freely distribute unicows.dll with your application, your licensing terms must meet certain conditions that no Open Source license can.
peer-reviewed and portable C++ source libraries. The libraries are intended to be widely useful, leveraging and extending both the C++ Standard Library and the Boost Libraries.
an event-driven networking framework supports TCP, UDP, SSL/TLS, multicast, Unix sockets, a large number of protocols (including HTTP, NNTP, IMAP, SSH, IRC, FTP, and others)