I don't use an online storage service. Like Don, I do use an online backup service, Crashplan. This market is heating up so you can expect features to get better and prices to get lower. I think I paid an intro fee of $60/year for 10 computers unlimited backup.
How much are you looking to store and how much do you plan to grow? Why are you looking to store online vs locally?
OneDrive, Google Drive, Dropbox all offer competitive plans. Most of the free plans aren't enough for much data. If you're an amazon prime member, you might want to look at their benefits. I think they offer free space for pictures in some form or another. I still don't have the need but have been tempted to look at Amazon's Cloud Drive.