Have you ever had a song stuck in your head that's driving you crazy, and you can't even remember what it's called? A simple application like SoundHound could really come in handy for those times, since it can recognize a song if you just play it - or even hum it - near your smartphone.
Once it has recognized the song (and it's very rare that it won't be able to), you can listen to a fragment of the result to make sure that it's what you were thinking of, and even view videoclips and other related material as long as you're connected to the Internet.
You can then broadcast your success on Facebook and Twitter, since the application is completely integrated with social networks.
SoundHound is one of the best applications of its category, since it is capable of recognizing almost any song that you play for it without any problems.