I have been using Dropbox for quite a while and can thoroughly recommend it. These days you need your data to be truly portable, with Dropbox you can store and sync your files from the cloud. If you are running a business or wanting to share files with friends Dropbox makes it very easy.
After signing up with Dropbox you get over 2 gigs of free storage and if you add others to Dropbox this can increase to 8 gigs. They also have a pay for option which increases your storage to 50 gigs. If you have an android or Iphone you can download the Dropbox app and have real data portability. I have included some useful articles showing you how to use and get the best out of Dropbox as well as a small video. Let me know how you use Dropbox.
I have just added a link to an interesting Mashable article on 5 ways to use Dropbox.