I liked this old blog post by Aysiu: The Linux community's mixed messages
I use s3cmd. Pure Python, small intuitive command-line, open source and cool
I don't know if you've had a chance to do this already, but I would use s3fs, and mount your s3 bucket as a normal file system. There is a fair amount of documentation on doing all of this. You can also use fstab to have it mount at boot. So backing up your files can be as easy as copy pasting into a file on your desktop.