Emailing files to Dropbox
Dropbox (referral link) is the service that Mobile Me should have been. Apple really missed the mark with MobileMe especially in the file syncing arena. Innovation does not tolerate a vacuum or even a partial suck. Dropbox filled that void nicely and the ubiquitous integration with iOS apps has made it indispensable. That's one reason I am a happy paying customer.
If I pay for a service, it's usually because I am deriving significant value from it.