I just discovered this great application that I think the BlackBerry truly needed. It is not really made for the BlackBerry but it works like a charm on my BlackBerry 8310. I am a (very) amateur musician when I have a few minutes to spare and this application ChordGenie has been a real help. It auto calculates over 1,000 chords for quite a few instruments. You can pick it up now for the current exchange rate of $10.28 (5 euros as of today). A trial is also available by heading over to wap.chordgenie.com from your BlackBerry.
Just look at the features at this link. Too many to copy and paste. You can even change the application to fit the banjo, ukulele, and mandolin. My favorite feature is the fact that it is fast and requires no internet connectivity.
I have posted some screenshots below for you to get an idea of the application: