The free app Bolt is my most used add-on app. I have had it since the day they released it. I can hit link on it where I can't in the BB Browser.

Other useful FREE apps I have are, Google Maps, Capturit (still works), BeBuzz Free so I never miss a phone call/voice
message, Starbucks (the SB employees are having so much fun with my phone), and Pipes game for an easy time killer.

Useful paid apps are, Repligo PDF Reader, CacheSense a must have nicety for Geocachers, Telenav, Berry Reader and HoneyDew which is a syncable shopping list.