Spark so many questions using this great representation of big data about population, global issues, environment etc. Check out Poodwaddle.com. Like Gapminder there are so many ways to use this data and avenues for students and adults alike to dig into big issues. The main dashboard gives you many options and when you click on a particular clock, for example the Earth Clock, 
you can look at the data beginning from now, today, a week, month and year. Every time I look at the numbers it makes me think deeply, question and want to know more. Be careful not to overwhelm younger students with it, it may require slower lead in.
How can we use big data like this?
How have you used Poodwaddle?
What other big data sites do you use for great learning and for sparking questions?