Qt by Digia

Qt ("cute") is a leading cross-platform application and UI development framework for leading desktop, embedded and mobile operating systems. Qt uses standard C++ and is widely used for developing software applications with a GUI and also for developing non-GUI applications with features such as file handling, database access, XML parsing, thread management and network support. Qt's powerful full-framework capabilities allows for the creation of highly-performing native applications as well as for hybrid development where the developer can choose which tools provide the best user experience.

Company Website: www.qt.digia.com