I also use my bell questions to have the students read the "extras" in their text book. In my World History text, each chapter ususally has a sidebar about art, people, geography to read followed by a few questions. I also ask open ended questions -
When is it okay to rebel against authority?
Does History have a point of view?
When is it okay for a nation to intervene in another nation's affairs?
What acts justify a nation's right to declare war?
I usually always start a new unit with this type of question - Tell me what you know about the French Revolution
On the day before testing I always use this one - List at least one thing your learn in this unit and why it was interesting to you
I also ask personal questions such as
What would you do with a million dollars?
If you could live anywhere in the world, where would you live and why?
Who do you admire the most and why?
Just a small sample of my bell questions - I have a ton since I have used them in World History, US History and Geography for the past 5 years.