Mozy, of course, is the quiet desktop tool that automatically copies your critical files to the cloud. I've been a user for years, and just this week I had to take advantage of it after a sudden system failure. Worked like a charm.
The app, which is free, enables you to access your files on the run. You can, for example, retrieve Word and Excel documents, view photos, and even play MP3s and certain kinds of videos.
Mozy also lets you share files via e-mail, or download them directly to your phone or tablet. (To access these options, you simply tap and hold any file. Unfortunately, you can't do likewise with folders.)
I do share his opinion that navigation could be better; drilling down through a folder structure is a less-than-ideal way to find the file(s) you want. At least there's a search option. (Lance noted that it didn't work with entire data sets, only individual folders, but in my tests that wasn't the case: you can indeed search from the top level.)
If you're already using a service like Dropbox or SugarSync to access files on the go, I'm not sure there's much point in switching to Mozy. But if you're a Mozy user, it's a no-brainer: grab this app. (If you're not a Mozy user, I can't recommend it highly enough--especially the free 2GB MozyHome account.)