http://www.netbeans.org/

NetBeans was updated yesterday. If you are not familiar with Netbeans, think of it as Sun's answer to Eclipse. NetBeans is a free, open-source IDE supporting several programming languages. Unlike Eclipse, the NetBeans support for languages other than Java is excellent.

NetBeans supported languages:
Java, C/C++, PHP, Python, JavaScript, Groovy, and Ruby.

NOTE: The Python support is labeled as 'Early Access 2'. I've used it and it seems fully integrated into the IDE with full functionality. The Python IDE can be downloaded separately from here:
http://www.netbeans.org/features/python/index.html

Supported technologies: Ajax, C/C++, Databases, Debugger, Desktop, Editor, Groovy, GUI Builder, Hudson, Java EE, JavaFX, Java ME, Java SE, JavaScript, Kenai, Maven, Mobile, PHP, Profiler, Python, Refactor, REST, Rich Client Platform, Ruby, SOAP, and Web (HTML, CSS, etc.).

The C/C++ IDE has all the bells and whistles you would expect: debugger, GUI builder, profiler, autocomplete, class browser, etc. Here's a full page of C/C++ features:
http://www.netbeans.org/features/cpp/index.html

The NetBeans IDE is easy to install and use straight out of the box and runs on many platforms including Windows, Linux, Mac OS X and Solaris.

Documentation and support is excellent:
http://wiki.netbeans.org/ (Wiki)
http://forums.netbeans.org/ (Forums)
http://plugins.netbeans.org/PluginPortal/ (Plugins)
Also, you can find tutorials on all supported technologies.

For C/C++, NetBeans is only one of several excellent IDEs that are available for the GCC compiler that are free and open-source. If you program in multiple languages, then NetBeans could very well be a best choice, because it allows using the same IDE interface for all of your languages and projects.