CodeLite is an open-source, cross platform IDE for the C/C++ programming languages. CodeLite is known to work on various OSs including:

Windows (XP SP3, 7, 8)
    Linux (Debian, Ubuntu, Fedora, OpenSUSE)
    Mac OSX (10.5.8)
    FreeBSD (installer not provided)

CodeLite is distributed under the terms of the GPLv2 license, with an exception for plugins.