We’ve been writing a lot about clever iPhone applications that add to the smartphone’s functionality. A couple of weeks back, we told you about Shazam, which helps you identify music by holding up your iPhone to a speaker. Within a few seconds, Shazam lets you see the name of the artist, song, and album info. We found another app that does a lot more -- and is also free.

iPhone 3G owners who haven’t yet downloaded Midomi from the App Store, this application is awesome because it helps you identify music in one of several ways: by singing a line or two from the song into the iPhone, by humming a few bars, by holding up the iPhone to a speaker to “listen” to a few seconds of a song, or by typing in a few keywords with your fingertip. You can also say some words, and the service can search its database looking for matches. If Midomi can recognize what you’re singing, humming or listening to, it will immediately give you the song info you seek, along with pointing you to the iTunes store to buy the track, if you want, or showing you related YouTube videos.

This thing works amazingly well, so be sure to check it out for yourself by downloading the free Midomi application for the iPhone 3G. Alternatively, you can sing or hum a few bars of a song you’re after via its PC-based Web site (computer microphone required).