Backblaze: Possibly world's easiest online backup (Invites)
No setup required. Really. Restoring is another question though.
I just got the preview for Backblaze, yet another online backup service. Or to use the current vernacular, cloud storage. It's a nifty service in that it does but one thing: back up your PC (Macs coming). Setup is so easy my cat could do it: you grab the software, run it, enter in an ID and password, and you're done.
By default, Backblaze begins to backup your PC in idle times, grabbing everything on your disk except the contents of your system and program directories, and your temp files. There's no storage or bandwidth limit, and it will store files up to 4GB in size. Backblaze costs $5 a month--quite reasonable.
If you want to change the default backup directories or filter out files by type, you can do that in the control panel. You can also change the backup schedule so the app isn't constantly waiting for idle time to send data. The service, as simple as it is, also gets geek cred for giving users the option to set a private encryption key for their data; if you use this option, even Backblaze won't be able to recover files if you lose your password. On the other hand, Backblaze can't access open files, which means it won't back up your Outlook e-mail unless you remember to close the app. Mozy handles Outlook better.
If you want a highly configurable backup solution, there are plenty of competitive options (Mozy, for instance, or Carbonite, which I use). Backblaze is the backup app you recommend to your mom, or anyone else who should be backing up their computer but is either too scared of the technicalities or too lazy to do the work necessary to make sure the app grabs all the files it needs to.
Backblaze will let users access files they've backed up from its Web site, but it is not designed for that. It's not a sharing or a syncing platform. And I'm not impressed by the restore services. Since the app doesn't back up your entire PC, you can't use it to do a bare-metal rebuild of a machine from backup. You can't even do a restore of all your data over the Web: You can get up to 1GB of data downloaded at a time (in Zip files--not exactly user-friendly), or 4.7GB on a DVD (for a fee), or, in a real catastrophe, up to 160GB on a USB hard drive sent by overnight mail to you (for more of a fee, but not a usurious one).
The service is still in private beta, but you can get access to the trial (15 days free) at https://www.backblaze.com/webware.