Is there any way in Outlook 2007 to get reminded more visually that my Out of Office is still on? Unfortunately there isn’t. The only notification that Outlook 2007 has, is the (temporary) balloon pop-up in the bottom and the (permanent) status bar notification.
Another way to go would be to create a recurring Task which reminds you to check the Out Of office status each morning (or whenever you start working 😉 . To create a recurring task choose; File-> New-> Task and in the Task window press the Recurrence button on the Ribbon. When the reminder pops-up in the morning, make sure you mark it as complete (right click on the task in the Reminder Window) instead of pressing the Dismiss button. This will make sure that there will be a new task generated for the next recurrence. Out Of office is still turned on.