I've tried out Copy.com and I really like it. It's very similar to Dropbox, but I think the interface is much smoother / cleaner.
If you sign up with my referral link below, you get 10GB free, +2GB for tweeting about it.
Even better though, they give you and the person that signs up 5GB free space (never expires) and right now there's no cap on how much free space you can get (I've seen people with over 2TB).