Josep just pointed out to me a post by TeamJordan23 on PinStack about a great J2ME graphing calculator for BlackBerry called XCalc. This is perfect for all of those times you need to graph the Cos, Sin, or Tangent while on the run. I just wish I had one of these in college. I might have been able to save a few bucks on a TI-82.
Seriously XCalc is a pretty cool program that you can pickup free on GetJar.com. The file is supposedly compatible with every BlackBerry but I have only tried it on my 8310. If a graphing calculator is not in your budget this may be a good bare bones alternative for casual calculations. They even have the sourcecode available on SourceForge if anybody is willing to port it natively to BlackBerry.
There are two download options for the app: