Shazam is a popular mobile application that allows you to discover what song is playing just by holding your phone to the speaker.
Shazam's online service provides an interesting way to connect with other users and share musical insights. You need to sign up for a free online account, and once you've done this, any songs that you tag using your mobile phone, will show up in your online Shazam account.
The My Shazam service is much like other social networks in that it allows you to invite friends and send messages. The difference here is that your profile is based around the kind of music you listen to with Shazam. Not only can you view the songs that your friends have tagged (and vice versa), but the site also gives you recommendations of music you might like, based on what you've tagged.
The Music Explorer feature of Shazam allows you to type the name of an artist or song and get a graphical representation of similar artists, which is a novel way of discovering stuff you might like. However, the explorer doesn't always find good matches, and sometimes the supposed similar artists are worlds apart.
You should note that the Shazam site doesn't actually include any song-matching functions itself. Instead it's merely a web-based companion for the mobile application.
The design of the Shazam web service is quite confusing and it's difficult to work out what you can do at first. However, fans of the Shazam service may find it a useful way to connect with other users.