I just got my iPhone a few weeks ago, so still learning about apps. So far, my favorites are Angry Birds (this game is addictive!), Navionics for a back-up GPS system on my boat, Red Laser for price checks, and Sky View to identify stars, planets, and constellations. Today I downloaded Gazelle from Quest Labs as a place to keep track of my medical info, doctors, medications, and so forth. I just started going to a new doctor, and it would have been nice to have had all this info organized while filling out the new patient paperwork. I'm anxious to learn about more apps to make the smart phone a more valuable tool for me. I also just loaded Flashlight. We got home from vacation last night after dark, and I had a hard time finding the keyhole. That will help!
Also, if you use your camera a lot, set up iCloud. It is so cool that it transfers your photos from the phone into a folder on your PC using your WiFi connection.