Dropbox is so simple. It makes you wonder why you didn't think of it yourself. When you sign up for an account, you're given a virtual box to drop anything you like into. It's password-protected and free with 2GB worth of storage. (Subscriptions are available for up to 100GB of storage for media-heavy users.)
Any file can be kept in Dropbox, which works like any other folder in your computer's system. You can even make specific Dropbox folders public for sharing with other Dropbox users. If you want to share a file with someone who does not use Dropbox, you can send them a link. This is a great way to share documents with coworkers or photos with grandparents.
Dropbox is about as universal as an app gets these days. It works with Mac, Windows, Linux, iPad, iPhone, Android and Blackberry, so files you create at home on the computer can be called up anywhere you've installed Dropbox.