If you own a Gmail account, then you have Google Drive. Same for Google Apps customers. It allows to store both Google Docs documents and files of whatever type. It's pretty useful (like any other cloud solution), and it comes with 5 free Gb, which is basically enough for simple documents. But you should avoid uploading your whole MP3 library.
Google Drive comes also with a very (too?) simple utility which synchronises a folder on your computer with your Drive account. There is also such a utility for iPhone, and for Android too.
But, if you have two accounts (e.g. one business and one personnal), then these utilities are not useful at all, since they support only one account at a time.
Hopefully, there is pretty good alternative: Insync. They also provide a synchronisation utility for Windows, Mac and Linux (beta). Mobile versions are coming.
The point here is that:
So to give it a try, go here.