If I ever meet the stranger who suggested I try Dropbox, I'll buy them ten beers. See, when Dropbox earned its place in my cloud storage feature, it also bagged itself a spot in the deepest recess of my aortic pump. For sharing files with friends and family, it's unrivalled in my opinion.
Its so simple: after installing Dropbox it creates a folder on your PC or Mac. Anything you copy into that folder gets uploaded to the Dropbox Web servers for backup, and if you have the software on more than one machine it'll automatically, and instantly, push a copy of those files down to those computers as well.
These files are private, but you also have a public folder, and this is where Dropbox comes into its own. Any files in your public dropbox have a standard HTTP URL. If you want to send a friend a zip file full of photos, or a rough mix of a home video you've been working on, just chuck it in your public folder and send them the HTTP link. They don't need a Dropbox account or any software -- the file just downloads.
By the way, did I mention this is all completely free?
Yes, I did. But it was a while ago, so let me reiterate. The basic account costs absolutely nothing, and is Dropbox's way of enticing you into its beautiful open arms. You get 2GB of storage and can upload and download as much as you want. When you need more space, it'll sell you 50GB of storage for $9.99 (about £6) per month, or 100GB for $19.99 (about £12) per month.
As someone who writes and records music, I accumulate a lot of files I want to share. As a result, Dropbox has become an essential tool. And honestly, if someone said I had to give up coffee or Dropbox... it'd be Dropbox. But only because without coffee, I wouldn't be awake to appreciate Dropbox.