I think it's a great tool to know another language and there should be more emphasis on learning an extra language from an early age. The younger you are the easier it is to pick another language up. One of my colleagues can speak fluent French, German and Italian which is mighty impressive!
My petite knowledge of French has helped me out a couple of times whilst I've been away in France, I have been able to put it to some good use :)
Can you speak any other languages?