A quick way to back up your blogspot hosted blog is to use the built in search tool to dump your blog’s entire contents. Using wget, this is something that could be easily incorporated into your nightly backup script. If you know your blog has fewer than 1000 entries, just use the following URL to dump everything in XML format:
From Google Operating System:
To download all the photos uploaded to your blog, DownThemAll comes to the rescue. The Firefox extension lets you download all the files with a certain extension from the current page, so it’s a good way to download all the images from the previous listing.
With the full XML feed and the images, it’s just a matter of writing a quick perl script to parse and import your entries into whatever format or system you wish to work with. –Link.