Computer World has a list of
10 Must Have Apps for your BlackberryComputerworld - Your BlackBerry might be plenty powerful out of the box, but there are hundreds of third-party applications out there that can make the device even more useful.
Adding the apps to your BlackBerry is a breeze, because they can all be installed "over the air," either by visiting the app's site with your BlackBerry's built-in browser and downloading the file directly, or by having an e-mail sent to your BlackBerry with a direct download link.
Even better, some of the best of these apps are totally free.
http://www.computerworld.com/s/article/9125000/10_must_have_free_BlackBerry_apps