You can use box to securely back up files in the cloud. You will then be able to access your files from any computer or mobile device or share files with others. You will receive 10 GB of storage free and the starter plan gives you 100 GB for $5 / month.
I'm pretty sure everyone knows about google drive! With Drive you get 15 GB of storage space. If you are only using it to share your freebie products, think about using it for back up also!
Again, you can access from anywhere -- unless your district blocks it! This has been my favorite for a couple years but I'm expanding to some of these others now. You only get 2GB free, but you can earn more by inviting your friends to sign up. Mine is up to 5.75 GB now. If you are not signed up for Dropbox, please use this link: https://db.tt/kTJYX3mC and I can earn a bit more space :)
I just started using bitcasa and am loving having 20 GB of storage. This is where I've chosen to back up my blogging files -- I would hate to lose them!
I just found multcloud in the last couple of weeks. It's not a cloud storage site, but a site that manages all your sites! Here is what mine looks like:
With this one account you can access all your storage folders, which saves a lot of time.
What would you add to this list?