Due to the fact I have two computers, a laptop, and an iPhone, there are some documents, pictures, and other things that I want to be able to access at any time on any of them, and not have to worry about manually transferring the updated versions of each file.
About a year ago, I discovered a service called DropBox, which is completely free. You can upgrade to paid accounts starting at $10 for 50GB of space. If you’re happy with 2GB, it’s free.
All you have to do is save the documents to your DropBox folder that you want synchronized to your other computers, and the service does it automatically. It even saves a secure copy of the files on the DropBox servers for remote access if you’re not near your computers.
Even if the other computers aren’t turned on, they’ll download the latest versions of the files when they are turned on.
I am so impressed by this service! When I update a file on my main computer, and my laptop is on, it synchronizes with my laptop, and in seconds, the file is updated in my laptop’s DropBox folder, too! It’s such a fantastic way service in the time and headaches it avoids!
If you’re not using this wonderful service, download it free from www.getdropbox.com
Tech Help 
Dropbox is pretty good. It’s a little slow sometimes (not a good way to move files if you’re in a hurry). I love it for collaboration with another author (via Track Changes in Word), though concurrent-use conflicts are a problem. It catches the error (saves a “conflicted copy) but you still have to reconcile them manually.
They should have a chat system so when you’re working in a folder with shared access to a little chat window opens, or some other flag is apparent, so it’s obvious the file is in use.
But for free, who’s complaining?!