Factmonster is a site that you can easily use with lower intermediate or even beginners.
http://www.factmonster.com/
The facts are short and simple, about all types of topics, ranging from sports to literature.
And the site also provides links for more advanced students to read more about the topics, which is useful if the students in your class are of different levels : some will remain on the first page, while others will go deeper into the subject.
Just remember to ask those who have the less information to speak first when they report to the class.