My husband recently recommended that I try Dropbox. It works kind of like a safety deposit box, in that your pictures are kept off site (off of your computer, DVD's or flash drivers), they're locked up safely, and you can access them whenever you like with your password.
It's the whole idea behind the "cloud". It simply means that instead of saving your pictures on something you own, you save them on someone else's server. Since you're looking at using this service only as a back-up, it might be worth a look.
The other thing I like is that I can put pictures in my Dropbox from my computer or my smartphone.
Hope that helps!