PlatformIO - Next-generation IDE for IoT
Eclipse - Eclipse is an open source community, whose projects are focused on building an open development platform comprised of extensible frameworks, tools and runtimes for building, deploying and managing software across the lifecycle.
UECIDE - Universal Embedded Computing IDE - UECIDE is aiming to be a generic IDE based on the Arduino IDE...
IntelliJ IDEA - Capable and Ergonomic IDE for JVM
Visual Micro - Arduino IDE for Visual Studio and Atmel Studio
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.