Carbonite (various pricing) is an excellent online backup program/service--once you have it configured. Version 4.0 assuages part of my mild discontent with previous versions by warning you on the very first page that .exe, video, and files over 4GB in size are not automatically selected for backup. Formerly, the lack of this warning meant that there was a real chance that a user might think that their family videos were being backed up while they were not.
I truly wish Carbonite had added an option to include these types of files. As it is, all file selection other than the automated selections is done via right-click in Windows Explorer. Even you when you add a folder explicitly in this manner, Carbonite skips the aforementioned file types. You must delve into the folder and add them, which is tedious at best. If you add more files of the excluded type to the folder you must again add them. There are other interface oddities, but they're all livable, and once you're acclimated, Carbonite is quite easy to use.
I think elements of the Carbonite interface are brilliant, such as the colored dots on the Windows Explorer file icons that let you know that files backup status. Also, the Carbonite drive found in My Computer lets you easily see what's being backed up and has been backed up in one location. There's now a dedicated restore routine which takes a bit of guesswork out of the process and if you're restoring from say XP to Windows 7, it will place files where they belong in the new OS. Friendly reminders are also forthcoming if your backups don't succeed for a few days.
Once you've configured Carbonite, it works great. In addition to the Windows client, the company provides clients for the iPad/iPhone/iPod Touch, Blackberry, Mac, and now Android phones. There's also Web access so you can download a file from virtually anywhere. The service is also priced competitively: $55 per year, per computer for unlimited backup. That's cheaper than Mozy's comparable plan.
Carbonite is a tough call for me. I truly like it, but the fact that you can't simply set it to watch a folder and be sure everything in it is backed up means there's a chance to lose data. If you're willing to do a little extra housekeeping, it's otherwise worthy.