OMG! no one has mentioned EVERNOTE.
www.evernote.com Amazing.
(I have jail broken my Iphone so I have access to some apps that blow anything away offered in the "app Store")
But my favorites,
Qik (Which allows me to record video streams live to the Qik website.) Works flawlessly.
Ocarina (In app store)
Pano (In App Store)
Cycorder (Jailbroken app) Full video recording to the iphone.
Clinometer (App Store)
Live Poker (app store)
For My 2 year old...
Animals,Vehicles, and Mooshake (She already takes my Iphone, slides it on, navigates to the screens where her apps are and plays them, then views the pictures and video on the phone, and always changes my settings for ringtones etc (House MD currently)