Even if wxWidgets is named here already:
wxWidgets!
Its a great and valuable Framwork (API, Class Library, whatever you may call it).
BUT: You can divide the functionality of this library into many small parts (base, core, gui, internet, xml) and use them, when necessary.
If you really want to make GOOD GUI applications, you have to use a GOOD API. wxWidgets is absolutly free (QT is not), only needs a small overhead in binary form, linked as dll or o-file is it about 2Megs, but has to offer all that you ever need to program great applications...
And wxWidgets is much more lighter than QT... and even better... :)
Try it...
