I still remember having to buy and flip through chord dictionaries when I used to play guitar. These days people have it easy with the internet and now Lil Ride Software has put all of those chords together into one BlackBerry app. Their LilGuitar app provides you with a chord dictionary including over 1400 chords. It even lets you hear the chords on 4 different types of guitars.
On touch screen phones you can just swipe your finger across the strings to hear what a chord sounds like. The app has a built in tuner that will play reference pitches in 6 different tuning systems to tune your guitar by ear. Its not automatic but it beats a tuning fork.