Netbeans - NetBeans IDE 7.0. Develop desktop, mobile and web applications with Java, PHP, C/C++ and more. Runs on Windows, Linux, Mac OS X and Solaris. NetBeans IDE is open-source and free.
Orwell Dev-C - The official site of the Bloodshed Dev-C++ update, which is fully portable, and optionally ships with a 64bit compiler.
Xamarin.Android - Integrated environment for building not only native Android but iOS and Windows apps too.
Qt Creator - Qt Creator is a cross-platform C++, JavaScript and QML integrated development environment. It is the fastest, easiest and most fun experience a C++ developer could wish for.
KDevelop - KDevelop is a free, open source IDE (Integrated Development Environment) for Linux, Solaris, FreeBSD, Mac OS X and other Unix flavors.
Rider - Rider is a cross-platform .NET IDE based on the IntelliJ platform and ReSharper.