libusb is a C library which provides generic access to USB devices. It supports Linux, OS X, Windows, Windows CE, Android, and OpenBSD/NetBSD.
MPC is a C library for the arithmetic of complex numbers with arbitrarily high precision and correct rounding of the result. It is built upon and follows the same principles as MPFR.
gtk-vector-screenshot is a GTK+ module that allows you to take a screenshot of a running GTK+ 3 application as a vector image, with fully scalable graphics and selectable text. It supports rendering the application to PDF, SVG, and PostScript.
libmodbus is a software library for sending/receiving data according to the Modbus protocol. It is written in C and supports RTU (serial) and TCP (Ethernet) communications.
Guile-AgentX is an AgentX implementation in Guile.
It makes it possible to monitor your software via SNMP.
A checking tool for gettext POT, PO, and MO files.
A fast little Web server for embedding.