Useless knowledge or topics for when the conversation is getting boring? Anyway, this page about things you probably don't know is really funny. The project is from UK, and teaches to the readers about many things, using original illustrations.
Check out some pictures:
The project was so succesfull that became a book:
More on the website: http://www.learnsomethingeveryday.co.uk - go to "Archive" to find other illustrations.