I would stay away from free cloud backups; they are notorious for disappearing with little or no warning. For only $5/mo or so, you can get unlimited backup space from Carbonite.com (disclaimer: I do not work for them, I'm just a satisfied customer). Mozy used to have a similar plan but recently discounted the unlimited part. CrashPlan's also has a similar plan but their servers are notoriously slow. Carbonite automatically works in the background to encrypt new data and upload it to their servers. Depending on your settings, you will never notice it working.
A caution about cloud backups. No media is fail safe. The cloud, HDDs, optical disks, flashdrives, etc. can all fail. To avoid a catastrophic loss, redundant backups are vital. One should have a minimum of two backups, at least one of which should be offsite. See here
(post #964) for the backup scheme I use. It may seem anal and expensive but it reasonably ensures that I will never use my data.