Do you have a small resolution screen and want to use QGIS? Then you know the problem of toolbars using up precious screen estate.

In QGIS 1.7

You find the option to make icons smaller (16×16) or bigger (32×32) in the options dialog:

Options dialog with icon size option

If you are running a version of QGIS < 1.7

You can change the size of toolbar icons to any value you like – smaller or bigger than by default. And this is how it’s done (in Python console):

from PyQt4.QtGui import QToolBar
from PyQt4.QtCore import QSize

toolbars = qgis.utils.iface.mainWindow().findChildren(QToolBar)
for toolbar in toolbars:

All toolbar icons will be scaled down to 16×16 pixels.

Kudos to Webrian on for this tip and to Nathan for pointing out how to access all toolbars.