Shazam (Site)– Another app featured on one of Apple’s commercials, this app will listen to a song for several seconds (user defined) and return the song, artist, and album title. You can tag it for download later in iTunes, personalize it with attached photos and share your tags via email. I found it to be very accurate and useful for those times when you just need to know who the heck that artist was. It can be less effective if there is a lot of ambient noise so if you are in a crowded bar, it may not work out so well.
This is a subjective list so you may very well have differing opinions on the choices but some of these are in the top 20 of all apps listed at the app store on iTunes. It also depends on your needs. There are lot of nice social networking apps out there as well but most require others to have the iPhone and the same app as well so it’s less practical for some users. If you think we’ve overlooked an app or want to share your opinions, hop on over to our forums to discuss.