I'm running Kubuntu 9.04 and trying to find the setting to turn off the popup that appears in the taskbar when you hover over an open application. I found that you can turn off the thumbnail under Desktop effects, but I want to remove it completely because it tends to get in the way. Does anyone know where this setting is, or if a setting exists to turn this off?

appears not possible yet - see kde-4-2-disable-ba ... 31977.html

If you want them off the task bar go into the task bar setting and disable the tooltips there.
I was able to disable popups over the tasks.
I still get it over kickoff but you can partially get rid of it anyway.

I can't find the taskbar settings. Is this in Kcontrol? I don't think Kubuntu uses Kcontrol and it isn't in the repositories.

The Taskbar settings are accessed by right clicking on a blank area of the Taskbar > Task Manager Settings.