Nobody will give that much away for free, because it's too much in bandwidth costs (as well as drive costs) to become free.
However, I can recommend two (quite) cheap options, JungleDisk and DropBox.
DropBox is a nice service that makes it very easy to sync your stuff between computers.
JungleDisk is just a nice app that uses Amazon S3 storage (rock-solid reliable).
As far as I'm aware, both are set up with encryption. Of course, I wouldn't trust this encryption for really sensitive stuff, and would recommend that you perform your own encryption client-side first.