wxWindows is a C++ cross-platform GUI toolkit which 
was started as a one man project by Julian Smart.
More information about wxWindows can be found at [1].
Currently, work is being done on these ports of wxWindows 2.X: 
        Windows (wxMSW, finished) 
        Unix, GTK+ (wxGTK, finished) 
        Unix, Motif (wxMotif, finished) 
        Macintosh (wxMac, advanced and preview available) 
        OS/2 (wxOS2, just started) 
        BeOS (wxBeOS, just started) 
        SciTech's MGL library (wxMGL, started a few months ago) 
This is the current stable (2.0.1) version of the GTK port [2].
There is also a CVS-Version, but it is beta.
Take a look into the samples/ directory of the working directory. 
It's very helpful.

- Alexander Langer
<alex@cichlids.com>

WWW:http://www.freiburg.linux.de/~wxxt/
And also see: http://web.ukonline.co.uk/julian.smart/wxwin/