The format for exporting is Atom, so for each post you'll get two files: one for the actual content of the post and one for the comments. There's also the option to save all the posts in a big Atom file.
Once you have all these files on your computer, you could write a tool that imports them to a database or use Blogger's API to recreate the blog. In fact, this tool also uses Blogger's API to get the feeds.
Another way to backup your blog involves manually downloading a page that contains all your blog posts and using an extension to get the photos from these posts.
{ via Digital Inspiration }
