The question has been closed for the following reason "The question is answered, right answer was accepted" by YamazaruNinja Aug 27 '10 at 02:23
Many great examples of irony are given in the Alanis Morissette song "Ironic" (http://www.google.com/search?q=ironic+song+lyrics). Here's a few from the song --
Basically, irony is something so drastically in opposition of what you're hoping for that it makes you heave a sign and think, "Well, that figures."
Irony isn't always depressing or frustrating. It's used to great effect in comedies and is the basis for a lot of humor.