After installation of Fedora Core 12, I couldn't find option "focus window on mouse over". In previous Fedora, there was Window Preferences in GNOME with following options: Window Selection, Titlebar Action and Movement Key. The solution was to install control-center-extra package.
First check if you have Windows option in Fedora Core 12 (just to be sure what's missing).
System -> Preferences -> Windows
If not you can't find Windows option, install the following package:
yum install control-center-extra
Package size is 59KB. After installation, Windows option should appear and you will be able to set roll-up window or select windows when the mouse moves over. Small but useful tip - I hope.

Very helpful tip, thanks. Saved me from having to search around.
Great information, I searched for this as well.
Thank you for posting this, it helped me solve the problem very quickly.
Why this was removed as a default install is a mystery.
Thank you, much appreciated.
Is there a way to roll-up (or shade, or fold) windows when mouse over (when mouse move over it will roll up or down, like being toggled!) ?
The cairo-dock, and other docks I think, do this. And several bars also. That would be a great workaround to Gimp tool bars that keep bothering... And to double click to roll up or down is too much effort
...
Btw, that control-center-extra does not seem available to ubuntu, I cant also find even its sources for version 2.30.2 (my current gnome on ubuntu).
Any tips on this?
thx!!
@teique - In GNOME 2.3 (Fedora Core 14) I can only check on Select windows when the mouse moves over them, so there isn't any other option. Maybe there is a hope with Compiz but in new GNOME 3, UI is completely redesigned and Compiz is not no more supported. I'm familiar with RedHat/Fedora distributions and only have heard that Ubuntu has "Unity" as UI (please correct me if I'm wrong), so I can't help you about Ubuntu ...
@dbunic

Indeed, to find a compiz workaround can be the solution, thx!
Btw, I like compiz a lot, so I will stick with the manager that has support for it
Also, I couldnt find a gnome forum to ask for this enhancement
I think this unity gui is at the latest ubuntu, but I preffer to stick to the long term supported stable releases; I think next one is next year..; so I am still with gnome