Best Cross Platform GUI Development Tool?

[Alma J Wetzker]

Looking for opinions here.

What is the best tool set for creating cross platform GUIs?  I need
something that that comes together fairly quickly and can access a
database backend.  Must run on Windoze (I will develop on linux.)  It
may be a web based application.  What should I use?  Why?

There are no right or wrong answers here, I just need to find something
vaguely familiar that I can throw an application together in a month or
so.  'C' is my favorite programming language.

TIA

    -- Alma