Is the storm your first BlackBerry? There are a million and one options so it really depends on your interests. I would recommended getting use to the functions and getting it set up the way you like it. From there maybe check out some themes to really customize the storm to your style. If you get curious about anything specific just throw it out there, if the Storm can do it, we can help you get it done!
What are you interested in? There is a lot of possibilities. I personally like a few apps that I can live without. BerryBuzz (changes the color of the led), BerryWeather (tells you the weather) and pattern lock (keeps your phone secure).