Functional languages: Real-life Examples

Question

Do functional languages bring anything in the resolution of everyday business problems?

Are there any successful projects that have been implemented using a function

Answer 1

Friends of mine use Haskell every day to implement financial algorithms.

Answer 2

Xmonad is a dynamically tiling X11 window manager that is written and configured in Haskell.

Facebook's chat feature makes heavy use of Erlang. http://www.facebook.com/note.php?note_id=14218138919&id=9445547199&index=0