I'm using SpiderOak which gives you 2GB free, but you can get an additional 1GB for each free referral, for a total of up to 5GB free. You get a 'zero-knowledge knowledge environment' (everything's encrypted on the client-side before upload, and they can't even see the file names or other meta-data). You can use an unlimited number of devices, sync folders between machines, no special 'dropbox' folder is required, share folders with others, and use their web interface (though I'm not sure what the implications of using that are on the 'zero-knowledge environment'...I don't know how they've designed that).