You have VisualTkinter also known as Visual Python. Development seems not active. You have sourceforge and googlecode sites. Web site is here.
On the other hand, you have PAGE that seems active and works in python 2.7 and py3k
As you indicate on your comment, none of these use the grid
geometry. As far as I can say the only GUI builder doing that could probably be Komodo Pro GUI Builder which was discontinued and made open source in ca. 2007. The code was located in the SpecTcl repository.
It seems to install fine on win7 although has not used it yet. This is an screenshot from my PC:
By the way, Rapyd Tk also had plans to implement grid geometry as in its documentation says it is not ready 'yet'. Unfortunately it seems 'nearly' abandoned.