An open source C++ GUI framework to make cross-platform programming child's play. Well, almost.
wxWidgets gives you a single, easy-to-use API for writing GUI applications on multiple platforms. Link with the appropriate library for your platform (Windows/Unix/Mac, others coming shortly) and compiler (almost any popular C++ compiler), and your application will adopt the look and feel appropriate to that platform. On top of great GUI functionality, wxWidgets gives you: online help, network programming, streams, clipboard and drag and drop, multithreading, image loading and saving in a variety of popular formats, database support, HTML viewing and printing, and much much more.
Support target platforms:
- Unix/Motif and X11
- Mac OS
Foreign libraries with wxWidgets bindings
- LibcURL - Internet URL (WWW, FTP, etc) access - Open Source - Current
- V2.8.12 (2011-03-28) 
Open Source - Library General Public License.