If you have a GMail account what you can do is add the calendar "Moon Phases" (its one of the special Gmail calendars anyone can add to their calendar), and then sync it with your phone. thats what I do and it will tell you a few weeks in advance what the moon phase will be. Plus its completely free! You just need to download google sync.
I have just uploaded my own app called LunarPhases to the mobihand site so should be available through crackberry app store within 24 hours.
It may be a little simpler than the previous app, you just enter a date and get a picture of the phases and a description, but then it is cheaper too only $0.99
(also Im pretty sure it wont work on touchscreen devices, but have made this a point with mobihand and they should not allow downloads for the storm devices)
Its nice when you live in the country, so you know when there will be light to do stuff at night, such as bonfires, cross country skiing, etc. or as was said before, hunting (not a nighttime activity).