Try Yahoo! Groups for backing up. I had just set up a Yahoo! group for my 2-person office because it was easier to share calendars between PC and Mac with no new software or learning curve. It is no cost and incredibly easy to set up. You are also able to restrict access and make the group invisible.
Once you set up your password and follow the easy steps to creating a group, you can upload your files into a secure area. Go to Files, click on Add File, Browse for your file and upload it. It is just as easy to delete it once you are back safe and sound at home.
I haven’t tried this myself, but it sounds like a simple solution, akin to using your Gmail account for storage.
I do want to caution anyone who tries it that data stored online is at risk both in transit (while you’re uploading and downloading) and while in storage. So I wouldn’t recommend putting anything super-sensitive up there unless you’ve encrypted it separately. As a quick way to get backed up without investing time and money into software and hardware, it’s definitely better than nothing.