Backing up your data is important, we all know that. However, backing up is often complicated and if your data isn't backed up and then stored off-site (i.e. not where your computer is) then your back up isn't truly safe. Enter Amazon's S3 service. Amazon has a bevy of computers waiting to hold your precious data in a safe, redundant, and off-site manner. Amazon charges a very low rate for bandwidth and storage and the best thing is that they have an API for developers to code against.
S3 Browser makes saving documents to and S3 'bucket' as simple as drag and drop. This app is open source, and started life as a diversion for the developer. Given those facts, S3 Browser is pretty slick.