The good old option is to use website ripping software like wget or HTTrack to create a mirror copy of any blog with images on your hard disk.
If that sounds too geeky, here's an excellent alternative - Greg Duncan has created a free blogger backup software that's extremely easy-to-use and gives lot of control over the backup process.
Related: Backup Blogger Posts on Wordpress
With Blogger Backup, you can backup your blog posts into a single file or one blog post per file or multiple posts per file. The future versions may even save your blog posts into PDF files that you can distribute as eBooks.
Blogger backup can download everything or you can do incremental backups meaning backup just the new posts since your last backup or download blog posts posted between any two given dates.
Best of all, Blogger Backup can also extract and save your Blog readers comments offline. No image support yet but you can always use Picasa web albums to download your Blogger photos.
codeplex.com/bloggerbackup [Uses the GData and Blogger Data API]