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)
an STL-like container for C++ that fills the gap between vector (or deque) and list, providing both fast random access and fast insertion/removal, all O(log n). This is not a map...
a font rendering library for OpenGL applications. It supports bitmap, textured, polygon, and outline glyph rendering and relies on FreeType for font loading.
a program that analyzes Python programs and detects various errors. It works by parsing the source file rather than importing it, so it is safe to use on modules with side effects. It's also much faster.