This page lists the latest N posts from the blog:
http://blogname.blogspot.com/search?max-results=N
Instead of N, type the number of posts. If your blog has less than 1000 posts, you can save this page:
http://blogname.blogspot.com/search?max-results=1000
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.
There's also a way to get all the posts in an XML feed. This is a better format if you intend to import it in a database.
http://blogname.blogspot.com/feeds/posts/default?max-results=1000
The number of posts can be easily obtained from the dashboard.
You can also backup the comments:
http://blogname.blogspot.com/feeds/comments/default?max-results=1000
