What is Dropbox?
A single secure place for file storage across all your devices (PC, Mac, iPhone, and Linux).
Why use it?
If you are the average computer user, you use multiple computers and have files scattered all over them. Has there ever been a time when you were at computer A and the file you needed was at computer B? Well, if you had Dropbox, then any file you placed inside the Dropbox file folder would have been automatically synced and on computer B already. Not to mention - on your iPhone too.
How much?
So, like totally free man. (for 2GB, which is a LOT of freaking files).
iPhone App?
It's awesome! You will have full access to files, pictures, videos, spreadsheets, and presentations all from within the Dropbox App. The files are not editable, mind you - but you can email a link to a file from within the app that can download/edited.
Trust me, you'll love it.