Microsoft Foundation Class Library (MFC)
Considering you are looking for a WINDOWS ONLY SOLUTION, (and that wxWidgets has been voted up on this thread) you may want to trade off some lightweight-ness and checkout MFC.
As far as Windows is concerned, MFC and wxWidgets seem to compete neck & neck, but overall, the former is lighter than the latter.
Some PROS:-
- MSVC MFC RAD support. Visual Studio arguably provides the best "RAD
tool & GUI lib" combo. The only other "dynamic duo" that comes close
is that of QtCreator & QT. wxSmith doesn't fully support all
- wxWidgets components, but it keeps improving. Very Very Rich set of
commercial GUI components.
- Free (but proprietary).
- Very nice when it comes to databound controls.
Some CONS:-
- The day you decide to port to other platforms, you will wish you had gone with a cross platform lib.
- Proprietary nature of MFC means you will have to navigate licencing very very carefully. But AFAIK, MFC is free to redistribute in binary form.
Here's a nice article touching on the "oil and water" that is "MFC and FLOSS applications". Apparently, they just might mix.
Anyways, appart from MFC, I think the FOX-Toolkit also deserves a mention, but just like FLTK, the major downside is lack of decent IDEs and RAD tools as compared to, say, QT or wxWidgets
