Go into your "options" on the main menu. Then click on "advanced options". From there go to "applications". This will give you a list of all the applications that are downloaded and installed on your BB.
You may want to be very careful of what you delete. If you aren't sure if you need it, or what it is used for... Don't delete it.
Posted from my CrackBerry at wapforums.crackberry.com