Since this thread was so fortuitously revived and I now have a smartphone again (had a company-supplied BB a few years ago), I'll toss in my $.02.

I have a Motorola Droid running Android 2.0

I use:

Droid Light (uses camera flash as LED flashlight)
Weatherbug
Google Voice (will let me make calls using an available WiFi internet connection if my cellular carrier is off-air)
Google maps with voice turnXturn nav and topo layer
Banking app (can transfer money between accounts in a pinch)
GeoPointer (Compass, Lat/Long)
MyTracks (overlays my movements on a local map; good for backtracking out of the woods)
Toddler Lock (interactive lights and sounds, keeps them from unlocking phone without unlock sequence; keeps them entertained in an emergency)

Under heavy usage conditions I can run my phone battery down in about 3-4 hours. To address this I have a Solio charger that can slowly solar charge its own battery then move that power to the phone battery. I also have a couple chargers from Energizer that let me run/charge the phone from AA batteries (I have a few of this size around), USB cable to charge from my laptop battery, and a car charger in each vehicle.