Symform is a cloud storage service which can give up to 200 GB of space, free of charge, if you're able to contribute some spare hard drive space of your own. You contribute 150GB of local storage to the grid, for instance, and you'll be able to use 100GB of the space provided by other users.
Sounds insecure? Don't worry, when you upload "Confidential.doc" the file isn't just sent to a single other computer. Instead it's encrypted, then scattered into tiny fragments and spread around the Symform grid.
The system has built-in redundancy, too. If one of your fragments is on a PC which crashes, or where the user deletes your files, or just uninstalls Symform, that's not a problem. Symform's Cloud Control service notices the failure, regenerates the files stored on that computer, and relocates them to other users.
There are still some complications. The grid obviously needs contributing devices to be available most of the time (80% at a minimum), for instance. And it'll generate more activity on your internet connection, too, as the system stores data on your PC and retrieves it at a later date (although the client does all you to control upload speeds so it won't use all your bandwidth).
If none of that sounds too appealing then the good news is that every Symform user gets 10GB of space free, whether they contribute local storage or not. Or you can just purchase drive space, which costs from a monthly $10 for 100GB.
It's a clever system; the file transfer client itself is very configurable; and overall the program could be a very cheap way to store lots of data elsewhere for very little cost. Will it work for you? The best way is to start with a free 10GB account and see how you get on.