We mentioned iStockManager a bit back as a free application that gave you access to your AMERITRADE account. Back then it was only available for the 8900, Storm, & Bold. Now they have opened up the doors to 8300 Curve and 8800 series devices.
Their app essentially gives you access to your TD AMERITRADE account where you can check the market and place trades (equity & options trading).
It also gives you access to streaming data, real time balances and positions, news and more. You can also check out the free MarketSimplified AMERITRADE application. I have never used either of them so let me know if you have.
You can pick up the latest version at istockmanager.com/blackberry/